Imaging system

ABSTRACT

An imaging system includes a light source emitting light at least a first excitation wavelength band to excite a first fluorescence material emitting a first fluorescence in a near-infrared wavelength band and light a second excitation wavelength band to excite a second fluorescence material emitting a second fluorescence in a visible wavelength band, a first image sensor receiving light including the first fluorescence and outputs a first imaging signal, a second image sensor receives light including the second fluorescence and output a second imaging signal, an optical element that separates the first fluorescence into a first optical branch and the second fluorescence into a second optical branch; and a pass filter in the first optical branch transmitting light having a near-infrared wavelength band and block light having a wavelength equal to or less than a predetermined wavelength belonging the visible wavelength band.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/324,675, filed Feb. 11, 2019, which is based on PCT filingPCT/JP2017/024582, filed Jul. 5, 2017, and claims priority to JapaneseApplication No. 2016-161544, filed Aug. 19, 2016, the entire contents ofeach are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an imaging system.

BACKGROUND ART

With the development of surgical methods and surgical instruments,surgery (so-called, microsurgery) for performing various treatmentswhile observing affected areas using medical observation apparatusessuch as endoscopes and surgical microscopes has been frequentlyperformed. In addition, such medical observation apparatuses are notlimited to apparatuses capable of optically observing affected areas,and apparatuses and systems displaying images of affected areas pickedup by image pickup apparatuses (cameras) or the like as electronicimages on display apparatuses, such as monitors, have also beenproposed.

Further, in recent years, an observation method using an observationapparatus such as an endoscope or a surgical microscope is not limitedto only a method of observing a surgical field using light in a band ofvisible light, and various observation methods called special lightobservation such as narrow band imaging (NBI), auto fluorescence imaging(AFI), and infrared imaging (IRI) have been proposed.

For example, in auto fluorescence imaging, a fluorescent material havingaffinity for a lesion such as cancer is previously administered to anexamination target person (patient), and excitation light for excitingthe fluorescent material is emitted, so that a lesion portion isobserved using a fluorescent image of fluorescence emitted from thefluorescent material accumulated in the lesion portion (that is, anobservation image based on a result of detection of fluorescence). Forexample, Patent Literature 1 discloses an example of an endoscopeapparatus capable of performing auto fluorescence imaging usingindocyanine green (ICG) as a fluorescent material.

CITATION LIST Patent Literature

Patent Literature 1: JP 3962122B

DISCLOSURE OF INVENTION Technical Problem

Incidentally, in recent years, various fluorescent materials other thanICG have been proposed as fluorescent materials which are used for autofluorescence imaging, and such fluorescent materials also includefluorescent materials emitting fluorescence having a wavelength banddifferent from that of ICG For example, ICG emits fluorescence having awavelength of approximately 820 nm (that is, light in a near-infraredband). On the other hand, fluorescent materials emitting fluorescence ina band of visible light such as fluorescein, 5-aminolevulinic acid(5ALA), and laserphyrin (registered trademark) have also been proposed.

Consequently, in the present disclosure, an imaging system is proposedwhich is capable of picking up a fluorescent image, corresponding to afluorescent material to be used, in a more suitable mode even under asituation where a plurality of types of fluorescent materials isselectively used.

Solution to Problem

According to the present disclosure, there is provided an imaging systemincluding: a light source apparatus which irradiates a predeterminedimage pickup target with light including a component in at least aportion of a wavelength band of an excitation wavelength of each of aplurality of types of fluorescent materials including a firstfluorescent material emitting fluorescence belonging to a near-infraredwavelength band and a second fluorescent material emitting fluorescencebelonging to a visible light wavelength band; and an image pickupapparatus which picks up an image acquired by a predetermined opticalsystem unit. The image pickup apparatus includes a branching opticalsystem that includes a dichroic film separating the light belonging tothe visible light wavelength band and the light belonging to thenear-infrared wavelength band from each other, a first image pickupelement which is provided at a stage after the branching optical systemand on which the light belonging to the near-infrared wavelength bandwhich is separated by the dichroic film is imaged, and a second imagepickup element which is provided at a stage after the branching opticalsystem and on which at least a portion of the light belonging to thevisible light wavelength band which is separated by the dichroic film isimaged, a fluorescent image of the fluorescence emitted from the firstfluorescent material is picked up by the first image pickup element, anda fluorescent image of the fluorescence emitted from the secondfluorescent material is picked up by the second image pickup element.

Advantageous Effects of Invention

As described above, according to the present disclosure, there isprovided an imaging system capable of observing a fluorescentobservation image, corresponding to a fluorescent material to be used,in a more suitable mode even under a situation where a plurality offluorescent materials are selectively used.

Note that the effects described above are not necessarily limitative.With or in the place of the above effects, there may be achieved any oneof the effects described in this specification or other effects that maybe grasped from this specification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view depicting an example of a schematic configuration of anendoscopic image pickup system according to an embodiment of the presentdisclosure.

FIG. 2 is a block diagram depicting an example of a functionalconfiguration of a camera head and a camera control unit (CCU) depictedin FIG. 1 .

FIG. 3 is a view depicting an example of a relationship between variousfluorescent materials used for auto fluorescence imaging and wavelengthbands of fluorescence emitted by the fluorescent materials.

FIG. 4 is a view depicting an example of schematic configurations of acamera head and a light source apparatus in an imaging system accordingto the embodiment.

FIG. 5 is a view depicting an example of a spectrum of light belongingto a visible light wavelength band and emitted from the light sourceapparatus according to the embodiment.

FIG. 6 is a schematic view depicting an example of a configuration ofthe camera head according to the embodiment.

FIG. 7 is a view depicting an example of a relationship between spectralcharacteristics of a dichroic film and various filters according to theembodiment and a spectrum of light emitted from the light sourceapparatus.

FIG. 8 is a schematic view depicting another example of a configurationof the camera head according to the embodiment.

FIG. 9 is a view depicting another example of a relationship betweenspectral characteristics of the dichroic film and various filtersaccording to the embodiment and a spectrum of light emitted from thelight source apparatus.

FIG. 10 is a schematic view depicting another example of a configurationof the camera head according to the embodiment.

FIG. 11 is a view depicting another example of a relationship betweenspectral characteristics of the dichroic film and various filtersaccording to the embodiment and a spectrum of light emitted from thelight source apparatus.

FIG. 12 is a view depicting characteristics of the camera head accordingto the embodiment.

FIG. 13 is a functional block diagram depicting a configuration exampleof a hardware configuration of an information processing apparatusconstituting the endoscopic image pickup system according to theembodiment of the present disclosure.

FIG. 14 is a view depicting an application example of the imaging systemaccording to the embodiment of the present disclosure.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, (a) preferred embodiment (s) of the present disclosure willbe described in detail with reference to the appended drawings. Notethat, in this specification and the appended drawings, structuralelements that have substantially the same function and structure aredenoted with the same reference numerals, and repeated explanation ofthese structural elements is omitted.

Note that a description will be given in the following order.

-   1. Configuration of endoscopic image pickup system-   2. Examination of auto fluorescence imaging-   3. Technical features-   3.1. Schematic configuration of camera head-   3.2. Configuration example 1 of two-plate type camera head-   3.3. Configuration example 2 of two-plate type camera head-   3.4. Configuration example of three-plate type camera head-   3.5. Operational effects-   4. Example of hardware configuration of CCU-   5. Application example-   6. Conclusion

1. CONFIGURATION OF ENDOSCOPIC IMAGE PICKUP SYSTEM

First, with reference to FIGS. 1 and 2 , an example of a schematicconfiguration of an endoscopic image pickup system according to anembodiment of the present disclosure is described. For example, FIG. 1is a view depicting an example of a schematic configuration of anendoscopic image pickup system to which the technology according to anembodiment of the present disclosure can be applied, and it illustratesan example in a case where the endoscopic image pickup system includes aso-called endoscopic surgery system. In FIG. 1 , a state is depicted inwhich a surgeon (medical doctor) 167 is using the endoscopic surgerysystem 100 to perform surgery for a patient 171 on a patient bed 169. Asdepicted, the endoscopic surgery system 100 includes an endoscope 101,other surgical tools 117, a supporting arm apparatus 127 which supportsthe endoscope 101 thereon, and a cart 137 on which various apparatusesfor endoscopic surgery are mounted.

In endoscopic surgery, in place of incision of the abdominal wall toperform laparotomy, a plurality of tubular aperture devices calledtrocars 125 a to 125 d is used to puncture the abdominal wall. Then, alens barrel 103 of the endoscope 101 and the other surgical tools 117are inserted into body cavity of the patient 171 through the trocars 125a to 125 d. In the example depicted, as the other surgical tools 117, apneumoperitoneum tube 119, an energy device 121 and forceps 123 areinserted into body cavity of the patient 171. Further, the energy device121 is a treatment tool for performing incision and peeling of a tissue,sealing of a blood vessel or the like by high frequency current orultrasonic vibration. However, the surgical tools 117 depicted are mereexamples at all, and as the surgical tools 117, various surgical toolswhich are generally used in endoscopic surgery such as, for example,tweezers or a retractor may be used.

An image of a surgical region in a body cavity of the patient 171 pickedup by the endoscope 101 is displayed on a display apparatus 141. Thesurgeon 167 would use the energy device 121 or the forceps 123 whilewatching the image of the surgical region displayed on the displayapparatus 141 on the real time basis to perform such treatment as, forexample, resection of an affected area. It is to be noted that, thoughnot depicted, the pneumoperitoneum tube 119, the energy device 121 andthe forceps 123 are supported by the surgeon 167, an assistant or thelike during surgery.

(Supporting Arm Apparatus)

The supporting arm apparatus 127 includes an arm unit 131 extending froma base unit 129. In the example depicted, the arm unit 131 includesjoint portions 133 a, 133 b and 133 c and links 135 a and 135 b and isdriven under the control of an arm controlling apparatus 145. Theendoscope 101 is supported by the arm unit 131 such that the positionand the posture of the endoscope 101 are controlled. Consequently,stable fixation in position of the endoscope 101 can be implemented.

(Endoscope)

The endoscope 101 includes the lens barrel 103 which has a region of apredetermined length from a distal end thereof to be inserted into abody cavity of the patient 171, and a camera head 105 connected to aproximal end of the lens barrel 103. In the example depicted, theendoscope 101 is depicted as a rigid endoscope having the lens barrel103 of the hard type. However, the endoscope 101 may otherwise beconfigured as a flexible endoscope having the lens barrel 103 of theflexible type.

The lens barrel 103 has, at a distal end thereof, an opening in which anobjective lens is fitted. A light source apparatus 143 is connected tothe endoscope 101 such that light generated by the light sourceapparatus 143 is introduced to a distal end of the lens barrel by alight guide extending in the inside of the lens barrel 103 and isemitted toward an observation target (in other words, an image pickuptarget) in a body cavity of the patient 171 through the objective lens.It is to be noted that the endoscope 101 may be a forward-viewingendoscope or may be an oblique-viewing endoscope or a side-viewingendoscope.

An optical system and an image pickup element are provided in the insideof the camera head 105 such that reflected light (observation light)from an observation target is condensed on the image pickup element bythe optical system. The observation light is photo-electricallyconverted by the image pickup element to generate an electric signalcorresponding to the observation light, namely, an image signalcorresponding to an observation image. The image signal is transmittedas RAW data to a camera control unit (CCU) 139. It is to be noted thatthe camera head 105 has a function incorporated therein for suitablydriving the optical system of the camera head 105 to adjust themagnification and the focal distance.

It is to be noted that, in order to establish compatibility with, forexample, a stereoscopic vision (three-dimensional (3D) display), aplurality of image pickup elements may be provided on the camera head105. In this case, a plurality of relay optical systems is provided inthe inside of the lens barrel 103 in order to guide observation light toeach of the plurality of image pickup elements.

(Various Apparatus Incorporated in Cart)

The CCU 139 includes a central processing unit (CPU), a graphicsprocessing unit (GPU) or the like and integrally controls operation ofthe endoscope 101 and the display apparatus 141. In particular, the CCU139 performs, for an image signal received from the camera head 105,various image processes for displaying an image based on the imagesignal such as, for example, a development process (demosaic process).The CCU 139 provides the image signal for which the image processes havebeen performed to the display apparatus 141. Further, the CCU 139transmits a control signal to the camera head 105 to control driving ofthe camera head 105. The control signal can include information relatingto an imaging condition such as a magnification or a focal distance.

The display apparatus 141 displays an image based on an image signal forwhich the image processes have been performed by the CCU 139 under thecontrol of the CCU 139. In a case where the endoscope 101 is ready forimaging of a high resolution such as 4K (horizontal pixel number3840×vertical pixel number 2160), 8K (horizontal pixel number7680×vertical pixel number 4320) or the like and/or ready for 3Ddisplay, then a display apparatus by which corresponding display of thehigh resolution and/or 3D display are possible can be used as thedisplay apparatus 141. In a case where the apparatus is ready forimaging of a high resolution such as 4K or 8K, if the display apparatusused as the display apparatus 141 has a size of equal to or not lessthan 55 inches, then a more immersive experience can be obtained.Further, a plurality of display apparatuses 141 having differentresolutions and different sizes may be provided in accordance withpurposes.

The light source apparatus 143 includes a light source such as, forexample, a light emitting diode (LED) and supplies irradiation light forimaging of a surgical region to the endoscope 101.

The arm controlling apparatus 145 includes a processor such as, forexample, a CPU and operates in accordance with a predetermined programto control driving of the arm unit 131 of the supporting arm apparatus127 in accordance with a predetermined controlling method.

An input apparatus 147 is an input interface for the endoscopic surgerysystem 100. A user can perform inputting of various kinds of informationor instruction inputting to the endoscopic surgery system 100 throughthe input apparatus 147. For example, the user would input various kindsof information relating to surgery such as physical information of apatient, information regarding a surgical procedure of the surgery andso forth through the input apparatus 147. Further, the user would input,for example, an instruction to drive the arm unit 131, an instruction tochange an imaging condition (type of irradiation light, magnification,focal distance or the like) by the endoscope 101, an instruction todrive the energy device 121 or the like through the input apparatus 147.

The type of the input apparatus 147 is not limited and may be that ofany one of various known input apparatuses. As the input apparatus 147,for example, a mouse, a keyboard, a touch panel, a switch, a foot switch157 and/or a lever or the like can be applied. In a case where a touchpanel is used as the input apparatus 147, it may be provided on thedisplay face of the display apparatus 141.

Otherwise, the input apparatus 147 is a device to be mounted on a usersuch as, for example, a glasses type wearable device or a head mounteddisplay (HMD), and various kinds of inputting are performed in responseto a gesture or a line of sight of the user detected by any of thedevices mentioned. Further, the input apparatus 147 includes a camerawhich can detect a motion of a user, and various kinds of inputting areperformed in response to a gesture or a line of sight of a user detectedfrom a video picked up by the camera. Further, the input apparatus 147includes a microphone which can collect the voice of a user, and variouskinds of inputting are performed by voice collected by the microphone.By configuring the input apparatus 147 such that various kinds ofinformation can be inputted in a contactless fashion in this manner,especially a user who belongs to a clean area (for example, the surgeon167) can operate an apparatus belonging to an unclean area in acontactless fashion. Further, since the user can operate an apparatuswithout releasing a possessed surgical tool from its hand, theconvenience to the user is improved.

A treatment tool controlling apparatus 149 controls driving of theenergy device 121 for cautery or incision of a tissue, sealing of ablood vessel or the like. A pneumoperitoneum apparatus 151 feeds gasinto a body cavity of the patient 171 through the pneumoperitoneum tube119 to inflate the body cavity in order to secure the field of view ofthe endoscope 101 and secure the working space for the surgeon. Arecorder 153 is an apparatus capable of recording various kinds ofinformation relating to surgery. A printer 155 is an apparatus capableof printing various kinds of information relating to surgery in variousforms such as a text, an image or a graph.

In the following, especially a characteristic configuration of theendoscopic surgery system 100 is described in more detail.

(Supporting Arm Apparatus)

The supporting arm apparatus 127 includes the base unit 129 serving as abase, and the arm unit 131 extending from the base unit 129. In theexample depicted, the arm unit 131 includes the plurality of jointportions 133 a, 133 b and 133 c and the plurality of links 135 a and 135b connected to each other by the joint portion 133 b. In FIG. 1 , forsimplified illustration, the configuration of the arm unit 131 isdepicted in a simplified form. Actually, the shape, number andarrangement of the joint portions 133 a to 133 c and the links 135 a and135 b and the direction and so forth of axes of rotation of the jointportions 133 a to 133 c can be set suitably such that the arm unit 131has a desired degree of freedom. For example, the arm unit 131 canpreferably be configured such that it has a degree of freedom equal toor not less than 6 degrees of freedom. This makes it possible to movethe endoscope 101 freely within the movable range of the arm unit 131.Consequently, it becomes possible to insert the lens barrel 103 of theendoscope 101 from a desired direction into a body cavity of the patient171.

An actuator is provided in each of the joint portions 133 a to 133 c,and the joint portions 133 a to 133 c are configured such that they arerotatable around predetermined axes of rotation thereof by driving ofthe respective actuators. The driving of the actuators is controlled bythe arm controlling apparatus 145 to control the rotational angle ofeach of the joint portions 133 a to 133 c thereby to control driving ofthe arm unit 131. Consequently, control of the position and the postureof the endoscope 101 can be implemented. Thereupon, the arm controllingapparatus 145 can control driving of the arm unit 131 by various knowncontrolling methods such as force control or position control.

For example, if the surgeon 167 suitably performs operation inputtingthrough the input apparatus 147 (including the foot switch 157), thendriving of the arm unit 131 may be controlled suitably by the armcontrolling apparatus 145 in response to the operation input to controlthe position and the posture of the endoscope 101. After the endoscope101 at the distal end of the arm unit 131 is moved from an arbitraryposition to a different arbitrary position by the control justdescribed, the endoscope 101 can be supported fixedly at the positionafter the movement. It is to be noted that the arm unit 131 may beoperated in a master-slave fashion. In this case, the arm unit 131 canbe remotely controlled by the user through the input apparatus 147 whichis placed at a place remote from the operating room.

Further, in a case where force control is applied, the arm controllingapparatus 145 may perform power-assisted control to drive the actuatorsof the joint portions 133 a to 133 c such that the arm unit 131 mayreceive external force by the user and move smoothly following theexternal force. This makes it possible to move, when the user directlytouches with and moves the arm unit 131, the arm unit 131 withcomparatively weak force. Accordingly, it becomes possible for the userto move the endoscope 101 more intuitively by a simpler and easieroperation, and the convenience to the user can be improved.

Here, generally in endoscopic surgery, the endoscope 101 is supported bya medical doctor called scopist. In contrast, where the supporting armapparatus 127 is used, the position of the endoscope 101 can be fixedmore certainly without hands, and therefore, an image of a surgicalregion can be obtained stably and surgery can be performed smoothly.

It is to be noted that the arm controlling apparatus 145 may notnecessarily be provided on the cart 137. Further, the arm controllingapparatus 145 may not necessarily be a single apparatus. For example,the arm controlling apparatus 145 may be provided in each of the jointportions 133 a to 133 c of the arm unit 131 of the supporting armapparatus 127 such that the plurality of arm controlling apparatus 145cooperate with each other to implement driving control of the arm unit131.

(Light Source Apparatus)

The light source apparatus 143 supplies irradiation light upon imagingof a surgical region to the endoscope 101. The light source apparatus143 includes a white light source which includes, for example, an LED, alaser light source or a combination of them. In this case, in a casewhere a white light source includes a combination of RGB laser lightsources, since the output intensity and the output timing can becontrolled with a high degree of accuracy for each color (eachwavelength), adjustment of the white balance of a picked up image can beperformed by the light source apparatus 143. Further, in this case, iflaser beams from the respective RGB laser light sources are emittedtime-divisionally on an observation target and driving of the imagepickup elements of the camera head 105 is controlled in synchronism withthe irradiation timings, then images individually corresponding to theR, G and B colors can be picked up time-divisionally. According to themethod just described, a color image can be obtained even if a colorfilter is not provided for the image pickup element.

Further, driving of the light source apparatus 143 may be controlledsuch that the intensity of light to be outputted is changed for eachpredetermined time. By controlling driving of the image pickup elementof the camera head 105 in synchronism with the timing of the change ofthe intensity of light to acquire images time-divisionally andsynthesizing the images, an image of a high dynamic range free fromso-called underexposed blocked up shadows and overexposed highlights canbe created.

Further, the light source apparatus 143 may be configured to be capableof supplying light of a predetermined wavelength band ready for speciallight observation. In special light observation, for example, byutilizing the wavelength dependency of absorption of light in a bodytissue to emit light of a narrower wavelength band in comparison withirradiation light upon ordinary observation (namely, white light),so-called narrow band light observation (narrow band imaging) of imaginga predetermined tissue such as a blood vessel of a superficial portionof the mucous membrane or the like in a high contrast is performed.Alternatively, in special light observation, fluorescent observation forobtaining an image from fluorescent light generated by emission ofexcitation light may be performed. In fluorescent observation, it ispossible to perform observation of fluorescent light from a body tissueby emitting excitation light on the body tissue (autofluorescenceobservation) or to obtain a fluorescent light image by locally injectinga reagent such as indocyanine green (ICG) into a body tissue andemitting excitation light corresponding to a fluorescent lightwavelength of the reagent upon the body tissue. The light sourceapparatus 143 can be configured to be capable of supplying suchnarrow-band light and/or excitation light suitable for special lightobservation as described above.

(Camera Head and CCU)

Functions of the camera head 105 of the endoscope 101 and the CCU 139are described in more detail with reference to FIG. 2 . FIG. 2 is ablock diagram depicting an example of a functional configuration of thecamera head 105 and the CCU 139 depicted in FIG. 1 .

Referring to FIG. 2 , the camera head 105 has, as functions thereof, alens unit 107, an image pickup unit 109, a driving unit 111, acommunication unit 113 and a camera head controlling unit 115. Further,the CCU 139 has, as functions thereof, a communication unit 159, animage processing unit 161 and a control unit 163. The camera head 105and the CCU 139 are connected to be bidirectionally communicable to eachother by a transmission cable 165.

First, a functional configuration of the camera head 105 is described.The lens unit 107 is an optical system provided at a connecting locationof the camera head 105 to the lens barrel 103. Observation light takenin from a distal end of the lens barrel 103 is introduced into thecamera head 105 and enters the lens unit 107. The lens unit 107 includesa combination of a plurality of lenses including a zoom lens and afocusing lens. The lens unit 107 has optical properties adjusted suchthat the observation light is condensed on a light receiving face of theimage pickup element of the image pickup unit 109. Further, the zoomlens and the focusing lens are configured such that the positionsthereof on their optical axis are movable for adjustment of themagnification and the focal point of a picked up image.

The image pickup unit 109 includes an image pickup element and isdisposed at a succeeding stage to the lens unit 107. Observation lighthaving passed through the lens unit 107 is condensed on the lightreceiving face of the image pickup element, and an image signalcorresponding to the observation image is generated by photoelectricconversion. The image signal generated by the image pickup unit 109 isprovided to the communication unit 113.

As the image pickup element which is included by the image pickup unit109, an image sensor, for example, of the complementary metal oxidesemiconductor (CMOS) type is used which has a Bayer array and is capableof picking up an image in color. It is to be noted that, as the imagepickup element, an image pickup element may be used which is ready, forexample, for imaging of an image of a high resolution equal to or notless than 4K. If an image of a surgical region is obtained in a highresolution, then the surgeon 167 can comprehend a state of the surgicalregion in enhanced details and can proceed with the surgery moresmoothly.

Further, the image pickup element which is included by the image pickupunit 109 is configured such that it has a pair of image pickup elementsfor acquiring image signals for the right eye and the left eyecompatible with 3D display. Where 3D display is applied, the surgeon 167can comprehend the depth of a living body tissue in the surgical regionmore accurately. It is to be noted that, if the image pickup unit 109 isconfigured as that of the multi-plate type, then a plurality of systemsof lens units 107 is provided corresponding to the individual imagepickup elements.

Further, the image pickup unit 109 may not necessarily be provided onthe camera head 105. For example, the image pickup unit 109 may beprovided just behind the objective lens in the inside of the lens barrel103.

The driving unit 111 includes an actuator and moves the zoom lens andthe focusing lens of the lens unit 107 by a predetermined distance alongthe optical axis under the control of the camera head controlling unit115. Consequently, the magnification and the focal point of a picked upimage by the image pickup unit 109 can be adjusted suitably.

The communication unit 113 includes a communication apparatus fortransmitting and receiving various kinds of information to and from theCCU 139. The communication unit 113 transmits an image signal acquiredfrom the image pickup unit 109 as RAW data to the CCU 139 through thetransmission cable 165. Thereupon, in order to display a picked up imageof a surgical region in low latency, preferably the image signal istransmitted by optical communication. This is because, upon surgery, thesurgeon 167 performs surgery while observing the state of an affectedarea through a picked up image, it is demanded for a moving image of thesurgical region to be displayed on the real time basis as far aspossible in order to achieve surgery with a higher degree of safety andcertainty. In a case where optical communication is applied, aphotoelectric conversion module for converting an electric signal intoan optical signal is provided in the communication unit 113. After theimage signal is converted into an optical signal by the photoelectricconversion module, it is transmitted to the CCU 139 through thetransmission cable 165.

Further, the communication unit 113 receives a control signal forcontrolling driving of the camera head 105 from the CCU 139. The controlsignal includes information relating to imaging conditions such as, forexample, information that a frame rate of a picked up image isdesignated, information that an exposure value upon imaging isdesignated and/or information that a magnification and a focal point ofa picked up image are designated. The communication unit 113 providesthe received control signal to the camera head controlling unit 115. Itis to be noted that also the control signal from the CCU 139 may betransmitted by optical communication. In this case, a photoelectricconversion module for converting an optical signal into an electricsignal is provided in the communication unit 113. After the controlsignal is converted into an electric signal by the photoelectricconversion module, it is provided to the camera head controlling unit115.

It is to be noted that the imaging conditions such as the frame rate,exposure value, magnification or focal point are set automatically bythe control unit 163 of the CCU 139 on the basis of an acquired imagesignal. In other words, what is called an auto exposure (AE) function,an auto focus (AF) function and an auto white balance (AWB) function areincorporated in the endoscope 101.

The camera head controlling unit 115 controls driving of the camera head105 on the basis of a control signal from the CCU 139 received throughthe communication unit 113. For example, the camera head controllingunit 115 controls driving of the image pickup element of the imagepickup unit 109 on the basis of information that a frame rate of apicked up image is designated and/or information that an exposure valueupon imaging is designated. Further, for example, the camera headcontrolling unit 115 suitably moves the zoom lens and the focus lens ofthe lens unit 107 through the driving unit 111 on the basis ofinformation that a magnification and a focal point of a picked up imageare designated. The camera head controlling unit 115 may further includea function for storing information for identifying the lens barrel 103or the camera head 105.

It is to be noted that, by disposing the components such as the lensunit 107 and the image pickup unit 109 in a sealed structure having highairtightness and waterproof, the camera head 105 can be provided withresistance to an autoclave sterilization process.

Now, a functional configuration of the CCU 139 is described. Thecommunication unit 159 includes a communication apparatus fortransmitting and receiving various kinds of information to and from thecamera head 105. The communication unit 159 receives an image signaltransmitted thereto from the camera head 105 through the transmissioncable 165. Thereupon, the image signal can be transmitted preferably byoptical communication as described above. In this case, for thecompatibility with optical communication, the communication unit 159includes a photoelectric conversion module for converting an opticalsignal into an electric signal. The communication unit 159 provides theimage signal after conversion into an electric signal to the imageprocessing unit 161.

Further, the communication unit 159 transmits, to the camera head 105, acontrol signal for controlling driving of the camera head 105. Thecontrol signal may also be transmitted by optical communication.

The image processing unit 161 performs various image processes for animage signal in the form of RAW data transmitted thereto from the camerahead 105. The image processes include various known signal processessuch as, for example, a development process, an image quality improvingprocess (a bandwidth enhancement process, a super-resolution process, anoise reduction (NR) process and/or an image stabilization process)and/or an enlargement process (electronic zooming process). Further, theimage processing unit 161 performs a detection process for an imagesignal in order to perform AE, AF and AWB.

The image processing unit 161 includes a processor such as a CPU or aGPU, and when the processor operates in accordance with a predeterminedprogram, the image processes and the detection process described abovecan be performed. It is to be noted that, in a case where the imageprocessing unit 161 includes a plurality of GPUs, the image processingunit 161 suitably divides information relating to an image signal suchthat image processes are performed in parallel by the plurality of GPUs.

The control unit 163 performs various kinds of control relating toimaging of a surgical region by the endoscope 101 and display of thepicked up image. For example, the control unit 163 generates a controlsignal for controlling driving of the camera head 105. Thereupon, in acase where imaging conditions are inputted by the user, then the controlunit 163 generates a control signal on the basis of the input by theuser. Alternatively, in a case where the endoscope 101 has an AEfunction, an AF function and an AWB function incorporated therein, thecontrol unit 163 suitably calculates an optimum exposure value, focaldistance and white balance in response to a result of a detectionprocess by the image processing unit 161 and generates a control signal.

Further, the control unit 163 controls the display apparatus 141 todisplay an image of a surgical region on the basis of an image signalfor which image processes have been performed by the image processingunit 161. Thereupon, the control unit 163 recognizes various objects inthe surgical region image using various image recognition technologies.For example, the control unit 163 can recognize a surgical tool such asforceps, a particular living body region, bleeding, mist when the energydevice 121 is used and so forth by detecting the shape, color and soforth of edges of the objects included in the surgical region image. Thecontrol unit 163 causes, when it controls the display apparatus 141 todisplay a surgical region image, various kinds of surgery supportinginformation to be displayed in an overlapping manner with an image ofthe surgical region using a result of the recognition. Where surgerysupporting information is displayed in an overlapping manner andpresented to the surgeon 167, the surgeon 167 can proceed with thesurgery more safety and certainty.

The transmission cable 165 which connects the camera head 105 and theCCU 139 to each other is an electric signal cable ready forcommunication of an electric signal, an optical fiber ready for opticalcommunication or a composite cable ready for both of electrical andoptical communication.

Here, while, in the example depicted, communication is performed bywired communication using the transmission cable 165, the communicationbetween the camera head 105 and the CCU 139 may be performed otherwiseby wireless communication. In a case where the communication between thecamera head 105 and the CCU 139 is performed by wireless communication,there is no necessity to lay the transmission cable 165 in the operatingroom. Therefore, such a situation that movement of medical staff in theoperating room is disturbed by the transmission cable 165 can beeliminated.

An example of the endoscopic surgery system 100 to which the technologyaccording to an embodiment of the present disclosure can be applied hasbeen described above. It is to be noted here that, although theendoscopic surgery system 100 has been described as an example, thesystem to which the technology according to an embodiment of the presentdisclosure can be applied is not limited to the example. For example,the technology according to an embodiment of the present disclosure maybe applied to a flexible endoscopic system for inspection or amicroscopic surgery system.

2. EXAMINATION OF AUTO FLUORESCENCE IMAGING

Next, a technical problem of the imaging system according to the presentembodiment will be described after describing an example of afluorescent material used for auto fluorescence imaging with regard tothe auto fluorescence imaging in which a fluorescent image of a lesionportion is observed using the fluorescent material, among observationmethods called special light observation.

In auto fluorescence imaging, a fluorescent material having an affinityfor a lesion such as cancer is previously administered to an examinationtarget person (patient), and excitation light for exciting thefluorescent material is emitted to observe a lesion portion using afluorescent image of fluorescence emitted from the fluorescent materialaccumulated in the lesion portion (that is, an observation image basedon a result of detection of fluorescence). A representative example of afluorescent material used for auto fluorescence imaging is indocyaninegreen (ICG). ICG emits fluorescence having a wavelength of approximately820 nm (that is, light in a near-infrared band) by using light having awavelength of approximately 808 nm as excitation light.

Further, in recent years, as fluorescent materials used for autofluorescence imaging, various fluorescent materials other than ICG havealso been proposed from the viewpoint of characteristics of moreselective accumulation on lesions such as cancer and a reduction in theinfluence (an adverse reaction) on an examination target person withadministration. In addition, among such fluorescent materials, afluorescent material emitting fluorescence in a wavelength banddifferent from that of ICG has also been proposed, and a fluorescentmaterial emitting light belonging to a visible light wavelength band hasalso been proposed. For example, FIG. 3 is a view depicting an exampleof a relationship between various fluorescent materials used for autofluorescence imaging and wavelength bands of fluorescence emitted by thefluorescent materials.

As a specific example, as depicted in FIG. 3 , in addition to ICGfluorescent materials emitting fluorescence in a band of visible lightsuch as fluorescein, 5-aminolevulinic acid (5ALA), and laserphyrin havealso been proposed as fluorescent materials used for auto fluorescenceimaging. More specifically, fluorescein emits fluorescence in a visiblelight region (particularly, a wavelength band of a G component) ofapproximately 520 nm. In addition, 5ALA emits fluorescence in a visiblelight region (particularly, a wavelength band of an R component) ofapproximately 635 nm. In addition, laserphyrin emits fluorescence in thevicinity of a wavelength band of 670 nm to 730 nm, that is, fluorescencefrom a visible light region (particularly, in the vicinity of anear-infrared region) to a near-infrared region. In addition, theexamples of the fluorescent materials depicted in FIG. 3 are onlyexamples, and various fluorescent materials other than the examplesdepicted in FIG. 3 have also been proposed. In particular, anear-infrared wavelength band in the vicinity of 650 nm to 1000 nm isknown as a wavelength band in which light easily passes through a livingbody, and is also called a “biological window”. For example, regarding awavelength band depicted as “reflected and transmitted light”, FIG. 3schematically depicts a wavelength band of light used in an analysismethod for analyzing components of a material serving as an observationtarget (in other words, an image pickup target) by emitting light in apredetermined wavelength band (particularly, light belonging to thebiological window) as in so-called near-infrared spectroscopy or thelike. For example, as fluorescent materials allowing a deeper portion inthe body of an examination target person to be observed using suchcharacteristics, various fluorescent materials emitting fluorescencebelonging to the biological window and a fluorescent material emittingfluorescence belonging to a wavelength band in the vicinity of thebiological window have also been proposed.

On the other hand, in auto fluorescence imaging, there is a tendency touse an image pickup apparatus (for example, a camera head) correspondingto a fluorescent material to be used for the pickup of a fluorescentimage of fluorescence emitted from the fluorescent material.Specifically, the fluorescence emitted from the fluorescent materialtends to have lower light intensity than other light such as visiblelight condensed together with the fluorescence and excitation light ofthe fluorescent material. For this reason, the image pickup apparatusmay be provided with, for example, a unique component (for example, abranching optical system, a filter, or the like) for separating at leasta portion of a wavelength band in a wavelength band of fluorescenceemitted from a fluorescent material and light (for example, visiblelight or excitation light) in another wavelength band different fromlight in the wavelength band. That is, a dedicated image pickupapparatus is often used for auto fluorescence imaging using apredetermined fluorescent material in order to observe a fluorescentimage of fluorescence emitted from the fluorescent material.

However, in a use mode in which a dedicated image pickup apparatus(camera head) is used for each fluorescent material in a situation wherevarious fluorescent materials (that is, a plurality of types offluorescent materials) are selectively used without being limited toICG, the image pickup apparatus is required to be attached and detached,which can make an operation related to auto fluorescence imaging morecomplicated. Further, it is necessary to prepare an image pickupapparatus for each fluorescent material to be used, which can result inan increase in costs. For this reason, the present disclosure proposesan imaging system which is capable of picking up a fluorescent image,corresponding to a fluorescent material to be used, even in a situationwhere a plurality of types of fluorescent materials is selectively usedby making it possible to observe fluorescence emitted from each of aplurality of types of fluorescent materials with one image pickupapparatus.

3. TECHNICAL FEATURES

Next, technical features of the imaging system according to theembodiment of the present disclosure will be described below.

3.1. Schematic Configurations of Camera Head and Light Source Apparatus

First, an example of schematic configurations of a camera head and alight source apparatus in the imaging system according to the presentembodiment will be described. For example, FIG. 4 is a view depicting anexample of schematic configurations of a camera head and a light sourceapparatus in an imaging system according to the embodiment. Note that,in the example depicted in FIG. 4 , in order to facilitate theunderstanding of the configurations of the camera head and the lightsource apparatus, the description will focus on a case in which afluorescent material administered to an examination target person inadvance is irradiated with excitation light from the skin without usingan endoscope or the like to pick up a fluorescent image of fluorescenceemitted from the fluorescent material, as an example of a simplerconfiguration. Further, in the example depicted in FIG. 4 , thedescription focuses on the light source apparatus 143 and the camerahead 105 in the imaging system according to the present embodiment, andother components are not depicted in the drawing. Note that, in theendoscopic image pickup system, strictly different portions can also bepresent as in a case in which some components such as an endoscope (lensbarrel) are inserted into the body cavity of an examination targetperson, but the schematic configuration thereof is the same as that inthe example depicted in FIG. 4 .

(Light Source Apparatus)

First, an example of a configuration of the light source apparatus 143will be described. As depicted in FIG. 4 , the light source apparatus143 according to the present embodiment includes a visible light source1431 that emits light (equivalent to an example of “first light”)belonging to a visible light wavelength band and a near-infrared lightsource 1433 that emits light (equivalent to an example of “secondlight”) belonging to a near-infrared wavelength band.

The visible light source 1431 is configured to be capable of emittinglight continuously distributed in a visible light wavelength band. Inaddition, the visible light source 1431 is configured to be capable ofemitting light having a peak of which the intensity is equal to orgreater than a predetermined threshold value at at least one or morepredetermined wavelength positions in a visible light wavelength band,and is configured to be capable of controlling the output (that is,intensity) of light corresponding to at least some wavelength positionsamong the at least one or more wavelength positions.

For example, FIG. 5 depicts an example of a spectrum of light belongingto a visible light wavelength band and emitted from the light sourceapparatus according to the embodiment, and is equivalent to a spectrumof light emitted by the visible light source 1431. In FIG. 5 , thehorizontal axis represents a wavelength, and the vertical axisrepresents the intensity of light by a relative value. In the exampledepicted in FIG. 5 , the visible light source 1431 is configured to becapable of emitting light (equivalent to an example of “fourth light”)which is continuously distributed in a visible light wavelength band andlight (equivalent to an example of “third light”) which has a peak ofwhich the intensity is higher than that of the light continuouslydistributed at a wavelength position in a wavelength band correspondingto each of an R component, a G component, and a B component.

More specifically, the visible light source 1431 includes a laser lightsource (equivalent to “an RGB laser light source”) which is configuredto be capable of outputting light having a peak at a wavelength positionin a wavelength band of each of the R component, the G component, andthe B component, and an LED light source (equivalent to “a white lightsource”, and hereinafter, also referred to as “a white LED”) which isconfigured to be capable of outputting white light. Note that, in thefollowing description, light having a peak at a wavelength position in awavelength band corresponding to each of an R component, a G component,and a B component emitted by the RGB laser light source may be simplyreferred to as “an R component”, “a G component”, and “a B component”.

Note that the visible light source 1431 may be configured to be capableof independently controlling the output of the RGB laser light sourceand the output of the white light source (white LED). In addition, theRGB laser light source may be configured to be capable of controllingthe output of at least some components among the R component, the Gcomponent, and the B component such as temporary attenuation ortemporary turn-off of the output. More specifically, the RGB laser lightsource is configured to be capable of controlling the output of lightcorresponding to at least a wavelength position which is included in awavelength band of fluorescence emitted from a predetermined fluorescentmaterial (particularly, a fluorescent material emitting fluorescencebelonging to a visible light wavelength band) among the R component, theG component, and the B component or which is positioned in the vicinityof the wavelength band of the fluorescence.

As a specific example, the RGB laser light source may be configured tobe capable of controlling the output of an R component as light at awavelength position which is included in a wavelength band offluorescence emitted from a fluorescent material, such as 5ALA orlaserphyrin, or which is positioned in the vicinity of the wavelengthband of the fluorescence. In addition, as another example, the RGB laserlight source may be configured to be capable of controlling the outputof a G component as light at a wavelength position which is included ina wavelength band of fluorescence emitted from a fluorescent material,such as fluorescein, or which is positioned in the vicinity of thewavelength band of the fluorescence. Naturally, the RGB laser lightsource may be configured to be capable of individually controlling theoutput of each of the R component, the G component, and the B componentor to be capable of performing control to be associated with at leasttwo or more components. In addition, the RGB laser light source may beconfigured to be capable of performing control so that the output ofeach of the R component, the G component, and the B component changescontinuously, or may be configured to be capable of switching betweenthe turn-on and turn-off of the output.

The near-infrared light source 1433 includes a light source which emitslight in a near-infrared wavelength band (that is, “a near-infraredlight source”), and is configured to be capable of emitting light in atleast a portion of a wavelength band in the near-infrared wavelengthband. More specifically, the near-infrared light source 1433 isconfigured to be capable of outputting light in a predeterminedwavelength band including at least a portion of a wavelength band of anexcitation wavelength of a predetermined fluorescent material(particularly, a fluorescent material excited by light belonging to anear-infrared wavelength band).

Based on such a configuration, in the imaging system according to thepresent embodiment, light belonging to a visible light wavelength bandand light belonging to a near-infrared wavelength band are emittedtoward an image pickup target from the light source apparatus 143. Inthis case, in the example depicted in FIG. 4 , for example, lightbelonging to a visible light wavelength band is reflected from thesurface of the skin of an examination target person and enters thecamera head 105 through an optical system unit 1054 to be describedlater. Similarly, among light beams belonging to a near-infraredwavelength band, light not belonging to a biological window is reflectedfrom the surface of the skin of the examination target person and entersthe camera head 105 through the optical system unit 1054.

On the other hand, among light beams belonging to a near-infraredwavelength band, light belonging to a biological window reaches theinside of the body through the skin of the examination target person,and is emitted to tissues inside the body such as blood vessels or lymphvessels. In this case, a fluorescent material, such as ICG, which hasbeen administered to the examination target person in advance andaccumulated in some tissues (for example, a lesion or the like) isexcited due to components in at least a portion of a wavelength bandamong light beams having reached the inside of the body of theexamination target person, and fluorescence is emitted from thefluorescent material. The fluorescence which is emitted from thefluorescent material (that is, fluorescence belonging to a near-infraredwavelength band) is emitted to the outside of the body through the skinof the examination target person and enters the camera head 105 throughthe optical system unit 1054.

(Camera Head and Optical System Unit)

Next, an example of schematic configurations of the camera head 105 andthe optical system unit 1054 will be described. As depicted in FIG. 4 ,the camera head 105 includes a branching optical system 201, filters 211and 213, an image pickup element for picking up a visible light image1051, an image pickup element for picking up a near-infrared light image1052, and an FPGA 1053. The camera head 105 is configured such that thepredetermined optical system unit 1054 can be mounted at the front stageof an incidence port toward the inside of the camera head 105. Inaddition, the camera head 105 is configured such that a notch filter1055 can be mounted at the front stage of the incidence port toward theinside of the camera head 105. Note that the notch filter 1055 may bemounted at the front stage of the optical system unit 1054 as denoted byreference numeral 1055 a. In addition, as another example, the notchfilter 1055 may be mounted to be interposed between the optical systemunit 1054 and the camera head 105 as denoted by reference numeral 1055b.

The optical system unit 1054 is a component for condensing externallight and guiding the condensed light into the camera head 105. Theoptical system unit 1054 includes an imaging optical system constitutedby, for example, a lens or the like, and causes the image pickup elementfor picking up the visible light image 1051 and the image pickup elementfor picking up the near-infrared light image 1052 which are providedinside the camera head 105 to image condensed light by the imagingoptical system. In other words, the optical system unit 1054 generatesan image of an image pickup target by taking in external light, andoutputs the generated image to the camera head 105 positioned at thesucceeding stage. In addition, the optical system unit 1054 may includean enlargement optical system that enlarges, for example, the generatedimage of the image pickup target. Specific examples of the opticalsystem unit 1054 include a detachable lens unit, a lens barrel in anendoscope, an objective lens in a microscope, and the like.

The notch filter 1055 is configured to be detachable from the frontstage of the camera head 105, and has a characteristic of blocking lightin a portion of a wavelength band among light beams entering the camerahead 105 through the optical system unit 1054. Note that a plurality oftypes of notch filters 1055 having different wavelength bands to beblocked may be selectively mounted on the camera head 105 or the opticalsystem unit 1054. As a specific example, the notch filter 1055 blockinglight in at least a portion of a wavelength band in an excitationwavelength of a fluorescent material in accordance with the fluorescentmaterial to be used may be mounted on the camera head 105 or the opticalsystem unit 1054. With such a configuration, it is possible to block theincidence of excitation light of the fluorescent material on the insideof the camera head 105 by the notch filter 1055 while simultaneouslypicking up a fluorescent image of fluorescence emitted from thefluorescent material.

Light guided to the inside of the camera head 105 through the opticalsystem unit 1054 is incident on the branching optical system 201. Thebranching optical system 201 is constituted by, for example, a prismincluding a dichroic film therein, and separates (branches) incidentlight into light belonging to a visible light wavelength band and lightbelonging to a near-infrared wavelength band. In addition, the branchingoptical system 201 guides the separated light belonging to the visiblelight wavelength band to the image pickup element for picking up thevisible light image 1051, and guides the separated light belonging tothe near-infrared wavelength band to the image pickup element forpicking up the near-infrared light image 1052.

In addition, the filter 211 is provided in a light path of the light(that is, a visible ray) which is separated by the branching opticalsystem 201 and is guided to the image pickup element for picking up thevisible light image 1051. The filter 211 mainly transmits lightbelonging to a visible light wavelength band, and has a characteristicof blocking at least light belonging to a near-infrared wavelength band.

In addition, a filter 213 is provided in a light path of the light (thatis, a near-infrared ray) which is separated by the branching opticalsystem 201 and is guided to the image pickup element for picking up thenear-infrared light image 1052. The filter 213 mainly transmits lightbelonging to a wavelength band including at least a portion of awavelength band of fluorescence emitted from a predetermined fluorescentmaterial (specifically, a fluorescent material emitting fluorescence ina near-infrared wavelength band such as ICG) in a near-infraredwavelength band, and has a characteristic of blocking at least lightbelonging to a visible light wavelength band.

Note that more details of a configuration corresponding to each of thenotch filter 1055, the branching optical system 201, and the filters 211and 213 will be separately described later with specific examples.

The image pickup element for picking up the visible light image 1051 isan image pickup element which is provided at the stage after thebranching optical system 201 and the filter 211 and on which lightseparated by the branching optical system 201 and belonging to a visiblelight wavelength band and having passed through the filter 211 isimaged. As the image pickup element for picking up the visible lightimage 1051, an image pickup element such as a CCD or a CMOS including anRGB color filter can be applied.

The image pickup element for picking up the near-infrared light image1052 is an image pickup element which is provided at the stage after thebranching optical system 201 and the filter 213 and on which lightseparated by the branching optical system 201 and belonging to at leasta portion of a wavelength band (in other words, a wavelength bandincluding at least a portion of a wavelength band of fluorescenceemitted from a predetermined fluorescent material) in a near-infraredwavelength band and having passed through the filter 213 is imaged. Itis preferable that an image pickup element having higher sensitivity beapplied as the image pickup element for picking up the near-infraredlight image 1052, and an image pickup element such as a CCD or a CMOSnot provided with a color filter may be applied.

The field-programmable gate array (FPGA) 1053 is equivalent to a controlunit that controls various operations of the camera head 105, andgenerates an image of an image pickup target on the basis of an imagepickup result of each of the image pickup element for picking up thevisible light image 1051 and the image pickup element for picking up thenear-infrared light image 1052. As a specific example, the FPGA 1053generates a visible light image of an image pickup target on the basisof an image pickup result obtained by the image pickup element forpicking up the visible light image 1051. In addition, the FPGA 1053generates a near-infrared light image of an image pickup target on thebasis of an image pickup result obtained by the image pickup element forpicking up the near-infrared light image 1052. Note that, in a case inwhich a fluorescent material emitting fluorescence belonging to anear-infrared wavelength region such as ICG is used, for example, it ispossible to obtain a fluorescence image of fluorescence emitted by thefluorescent material as the near-infrared light image generated by theimage pickup element for picking up the near-infrared light image 1052.In addition, the FPGA 1053 may generate an image in which anear-infrared light image (in other words, a fluorescence image) basedon the image pickup result obtained by the image pickup element forpicking up the near-infrared light image 1052 is superimposed on avisible light image based on the image pickup result obtained by theimage pickup element for picking up the visible light image 1051.

Note that it is more preferable that the image pickup element forpicking up the visible light image 1051 be disposed such that an opticalaxis of a visible ray emitted from the branching optical system 201 andhaving passed through the filter 211 is imaged in the center thereof. Inaddition, regarding the image pickup element for picking up thenear-infrared light image 1052, it is more preferable that a fixedposition be determined while performing shift adjustment in a directionperpendicular to an optical axis so that a screen deviation of anear-infrared light image with respect to a visible light imagegenerated on the basis of the image pickup result of the image pickupelement for picking up the visible light image 1051 is minimized. Withsuch a configuration, it is possible to perform alignment of the visiblelight image and the near-infrared light image (fluorescence image) moresimply at the time of superimposing the images on each other. Inaddition, as another example, the magnitude of a screen deviation of anear-infrared light image (fluorescence image) with respect to a visiblelight image generated due to a product error may be specified in advanceafter determining a fixed position of the image pickup element forpicking up the near-infrared light image 1052 without performing theabove-described position adjustment, and a read-out starting position ofa near-infrared light image signal may be shifted so that the specifiedmagnitude of the screen deviation is minimized. It is possible to omitthe above-described adjustment processing by adopting a method ofadjusting a read-out starting position, which leads to an advantage interms of costs.

An example of schematic configurations of the camera head and the lightsource apparatus in the imaging system according to the presentembodiment has been described above with reference to FIGS. 4 and 5 .Note that an example of a more detailed configuration of a camera headin the imaging system according to the present embodiment will bedescribed below with regard to a case in which the camera head isconfigured as a two-plate type camera head and a case in which thecamera head is configured as a three-plate type camera head.

3.2. Configuration Example 1 of Two-Plate Type Camera Head

First, as an example of a configuration of a camera head in the imagingsystem according to the present embodiment, a description will be givenof an example of a configuration of a two-plate type camera head,particularly, focusing on a configuration until incident light is imagedon an image pickup element through a branching optical system. Forexample, FIG. 6 is a schematic view depicting an example of aconfiguration of a camera head according to the present embodiment. Notethat, in the following description, the camera head 105 depicted in FIG.6 may be referred to as “a camera head 105 a” in a case in which thecamera head 105 is expressly shown.

As depicted in FIG. 6 , the camera head 105 a includes a colorseparation prism 201 a, an image pickup element for picking up thevisible light image 1051, an image pickup element for picking up thenear-infrared light image 1052, a notch filter 1055, a short pass filter211, and a long pass filter 213. Note that the image pickup element forpicking up the visible light image 1051 and the image pickup element forpicking up the near-infrared light image 1052 have the sameconfigurations as those of the image pickup element for picking up thevisible light image 1051 and the image pickup element for picking up thenear-infrared light image 1052 described with reference to FIG. 4 , andthus a detailed description thereof will be omitted.

The color separation prism 201 a is an optical member that separatesincident light incident on the camera head 105 a into light belonging toa visible light wavelength band and light belonging to a near-infraredwavelength band, and is equivalent to an example of the branchingoptical system 201 depicted in FIG. 4 . In addition, a dichroic film 203for separating light belonging to a visible light wavelength band andlight belonging to a near-infrared wavelength band from each other isprovided inside the color separation prism 201 a.

Specifically, as depicted in FIG. 6 , the color separation prism 201 ais a prism in which a first prism 205 and a second prism 207 are bondedto each other through the dichroic film 203. That is, the dichroic film203 is provided at an interface between the first prism 205 and thesecond prism 207.

The dichroic film 203 is an optical film that separates incident lightincident on the color separation prism 201 a and including lightbelonging to a visible light wavelength band and light belonging to anear-infrared wavelength band into light belonging to a visible lightwavelength band and light belonging to a near-infrared wavelength band.Specifically, the dichroic film 203 has a characteristic of reflectinglight belonging to a visible light wavelength band and transmittinglight belonging to a near-infrared wavelength band. Note that details ofspectral characteristics of the dichroic film 203 will be separatelydescribed later.

The first prism 205 is a prism functioning as a light path for visiblelight on which light belonging to a visible light wavelength band andlight belonging to a near-infrared wavelength band is incident (that is,incident light) are incident and through which light belonging to avisible light wavelength band is guided. In addition, the second prism207 is a prism functioning as a light path for near-infrared light towhich light belonging to a near-infrared wavelength band is guided.

Incident light incident on the first prism 205 travels straight insidethe first prism 205 and is separated into light belonging to a visiblelight wavelength band and light belonging to a near-infrared wavelengthband by the dichroic film 203 which is obliquely provided on the opticalaxis thereof.

The light belonging to a visible light wavelength band is reflected bythe dichroic film 203 and is guided to the inside of the first prism205. Here, the reflected and separated light belonging to a visiblelight wavelength band (that is, a visible ray) is totally reflected at aposition A depicted in FIG. 6 only once and is transmitted to theoutside of the first prism 205. Thereby, it is possible to bring anangle of a film formation surface of the dichroic film 203 with respectto the optical axis close to a right angle. Conversely, an installationangle on the optical axis of the dichroic film 203 according to thepresent embodiment is set such that a total reflection condition ofvisible rays at the position A is established. The dichroic film 203 isdisposed in this manner, so that it is possible to suppress changes inspectral characteristics of the dichroic film 203 due to a difference inan incidence angle between an upper light beam and a lower light beamand to perform wavelength separation with a high level of accuracy evenwhen a bright light beam having an F value is incident on the firstprism 205.

Visible rays having passed through the first prism 205 are guided to theimage pickup element for picking up the visible light image 1051. Inthis case, the short pass filter 211 is provided in a light path oflight which is separated by the dichroic film 203 and is imaged on theimage pickup element for picking up the visible light image 1051. Theshort pass filter 211 transmits light (that is, light including visiblelight) having a wavelength equal to or less than a boundary between avisible light wavelength band and a near-infrared wavelength band with750 nm as the boundary therebetween, and blocks light (that is, lightincluding near-infrared light) having a wavelength exceeding theboundary. With such a configuration, it is possible to exclude infraredlight included in visible rays having passed through the first prism 205and to improve color reproducibility of a visible light image.

On the other hand, light belonging to a near-infrared wavelength bandand having passed through the dichroic film 203 is incident on thesecond prism 207 and travels straight inside the second prism 207. Anend surface (in other words, an emitting surface on a downstream side ofthe optical axis of the second prism 207) on a side opposite to the sidewhere the dichroic film 203 is provided in the second prism 207 isprovided so as to be perpendicular to the optical axis, and lightbelonging to a near-infrared wavelength band is transmitted to theoutside of the second prism 207 while maintaining a state where thelight is perpendicular to the emitting surface of the second prism 207.

Near infrared rays having passed through the second prism 207 are guidedto the image pickup element for picking up the near-infrared light image1052. In this case, the long pass filter 213 is provided in a light pathof light which is separated by the dichroic film 203 and is imaged onthe image pickup element for picking up the near-infrared light image1052. The long pass filter 213 has a characteristic of opposite polarityto that of the short pass filter 211. That is, the long pass filter 213transmits light (that is, light including near-infrared light) having awavelength equal to or greater than a boundary between a visible lightwavelength band and a near-infrared wavelength band with 750 nm as theboundary therebetween, and blocks light (that is, light includingvisible light) having a wavelength less than the boundary. With such aconfiguration, it is possible to exclude visible light included in nearinfrared rays having passed through the second prism 207.

Note that a material of the color separation prism 201 a according tothe present embodiment is not particularly limited, and it is possibleto appropriately use known optical glass or optical crystal inaccordance with a wavelength of light guided to the inside of the colorseparation prism 201 a.

In addition, the notch filter 1055 is configured to be detachable fromthe front stage of the color separation prism 201 a. With such aconfiguration, for example, as the notch filter 1055, it is possible tomount a filter having a characteristic of blocking light in at least aportion of a wavelength band of an excitation wavelength of afluorescent material in accordance with the fluorescent material to beused. As a more specific example, in a case in which ICG is used as afluorescent material, a filter blocking light in the vicinity of 808 nmwhich is an excitation wavelength of ICG may be mounted as the notchfilter 1055.

As an example of a configuration of a camera head in the imaging systemaccording to the present embodiment, reference has been made to FIG. 6above to describe an example of a configuration of a two-plate typecamera head, particularly, focusing on a configuration until incidentlight is imaged on an image pickup element through a branching opticalsystem. Note that the configuration of the camera head described in FIG.6 is merely an example and is not necessarily limited to the exampledepicted in FIG. 6 . For example, the installation position of the imagepickup element for picking up the visible light image 1051 and theinstallation position of the image pickup element for picking up thenear-infrared light image 1052 may be reversed. In this case, forexample, as the dichroic film 203, a dichroic film having acharacteristic of transmitting light belonging to a visible lightwavelength band and reflecting light belonging to a near-infraredwavelength band may be applied. That is, the characteristic of thedichroic film 203 may be appropriately changed in accordance with arelationship between the installation position of the image pickupelement for picking up the visible light image 1051 and the installationposition of the image pickup element for picking up the near-infraredlight image 1052.

Subsequently, spectral characteristics of the dichroic film 203, thenotch filter 1055, the short pass filter 211, and the long pass filter213 in the camera head 105 a will be described with reference to FIG. 7. FIG. 7 is a view depicting an example of a relationship betweenspectral characteristics of a dichroic film and various filtersaccording to the present embodiment and a spectrum of light emitted froma light source apparatus. For example, in the upper drawing of FIG. 7 ,spectral characteristics of the dichroic film 203, the notch filter1055, the short pass filter 211, and the long pass filter 213 areschematically depicted. In the upper drawing of FIG. 7 , the horizontalaxis represents a wavelength, and the vertical axis representscharacteristics according to transmission or reflection of the dichroicfilm and various filters by relative values (%). In addition, the lowerdrawing of FIG. 7 depicts a spectrum of light emitted from the lightsource apparatus according to the present embodiment. In the lowerdrawing of FIG. 7 , the horizontal axis represents a wavelength, and thevertical axis represents characteristics according to transmission orreflection of the dichroic film and various filters by relative values(%). Note that, in FIG. 7 , the position of the horizontal axis in theupper drawing and the position of the horizontal axis in the lowerdrawing correspond to each other. Further, in the present description,it is assumed that the light source apparatus emits light (that is,excitation light of ICG) in the vicinity of 808 nm which is anexcitation wavelength of ICG as light in a near-infrared wavelengthband. That is, in the example depicted in FIG. 7 , a notch filterblocking light in the vicinity of 808 nm which is an excitationwavelength of ICG is applied as the notch filter 1055.

In FIG. 7 , a graph plotted as dichroic film characteristicsschematically depicts a wavelength band of each of light reflected bythe dichroic film 203 depicted in FIG. 6 and light passing through thedichroic film 203. Specifically, the inner side of the graph plotted asdichroic film characteristics is equivalent to a component reflected bythe dichroic film 203, and the outer side of the graph is equivalent toa component passing through the dichroic film 203. That is, the dichroicfilm 203 has a characteristic of reflecting most (for example, equal toor greater than 90%) of light in a wavelength band of 350 nm to 750 nmand transmitting most (for example, equal to or greater than 90%) oflight in a wavelength band exceeding 750 nm.

In addition, a graph plotted as characteristics of the short pass filterschematically depicts a wavelength band of each of light passing throughthe short pass filter 211 depicted in FIG. 6 and light blocked by theshort pass filter 211. As described above, the short pass filter 211transmits light (that is, light including visible light) having awavelength equal to or less than a boundary between a visible lightwavelength band and a near-infrared wavelength band with 750 nm as aboundary therebetween, and blocks light (that is, light includingnear-infrared light) having a wavelength exceeding the boundary. Withsuch a configuration, it is possible to image, for example, light,belonging to a visible light wavelength band, which is emitted from thevisible light source 1431 of the light source apparatus 143 and isguided to the inside of the camera head 105 a on the image pickupelement for picking up the visible light image 1051 through the colorseparation prism 201 a and the short pass filter 211.

In addition, a graph plotted as characteristics of the long pass filterschematically depicts a wavelength band of each of light passing throughthe long pass filter 213 depicted in FIG. 6 and light blocked by thelong pass filter 213. As described above, the long pass filter 213transmits light (that is, light including near-infrared light) having awavelength equal to or greater than a boundary between a visible lightwavelength band and a near-infrared wavelength band with 750 nm as theboundary therebetween, and blocks light (that is, light includingvisible light) having a wavelength less than the boundary. With such aconfiguration, it is possible to image, for example, light, belonging toa near-infrared light wavelength band, which is emitted from thenear-infrared light source 1433 of the light source apparatus 143 andincident into the camera head 105 a on the image pickup element forpicking up the near-infrared light image 1052 through the colorseparation prism 201 a and the long pass filter 213.

On the other hand, in the example depicted in FIG. 7 , a filter blockinglight in the vicinity of 808 nm which is an excitation wavelength of ICGis mounted at the front stage of the color separation prism 201 a as thenotch filter 1055. For this reason, light in the vicinity of 808 nmwhich is an excitation wavelength of ICG among light beams belonging toa near-infrared wavelength band which are guided to the inside of thecamera head 105 a, is blocked by the notch filter 1055.

Based on the above-described configuration, the camera head 105 a canpick up, for example, a fluorescent image of fluorescence belonging to anear-infrared wavelength band and emitted from a fluorescent materialsuch as ICG or a fluorescent image of fluorescence belonging to avisible light wavelength band and emitted from a fluorescent materialsuch as 5ALA and laserphyrin.

As a specific example, a description will be given focusing on a case inwhich ICG is used as a fluorescent material. As depicted in FIG. 7 ,fluorescence emitted from ICG belongs to a near-infrared wavelengthband, and thus the fluorescence is incident into the camera head 105 aand is then imaged on the image pickup element for picking up thenear-infrared light image 1052 through the color separation prism 201 aand the long pass filter 213. In addition, excitation light of ICG isblocked by the notch filter 1055 before being incident into the camerahead 105 a. With such a configuration, it is possible to observe afluorescent image of fluorescence emitted from ICG using a near-infraredlight image generated on the basis of an image pickup result obtained bythe image pickup element for picking up the near-infrared light image1052. Further, in a case in which ICG is used as a fluorescent material,it is possible to pick up a visible light image of an image pickuptarget independently of a fluorescent image of fluorescence emitted fromICG on the basis of an image pickup result obtained by the image pickupelement for picking up the visible light image 1051. For this reason, inthis case, for example, it is also possible to superimpose thefluorescent image of fluorescence emitted from ICG on the visible lightimage of the image pickup target.

Subsequently, a description will be given focusing on a case in which5ALA is used as a fluorescent material. As depicted in FIG. 7 ,fluorescence emitted from 5ALA belongs to a visible light wavelengthband, and thus the fluorescence is incident into the camera head 105 aand is then imaged on the image pickup element for picking up thevisible light image 1051 through the color separation prism 201 a andthe short pass filter 211. On the other hand, at least a portion of awavelength band of fluorescence emitted from 5ALA overlaps a wavelengthband of an R component. For this reason, in a case in which afluorescent image of fluorescence emitted from 5ALA is picked up, atleast the output of an R component emitted from an RGB laser lightsource of the visible light source 1431, in light belonging to a visiblelight wavelength band and emitted from the visible light source 1431 ofthe light source apparatus 143, may be limited (for example, set to bein an off-state). Based on such a configuration and control, it ispossible to observe a fluorescent image of fluorescence emitted from5ALA using a visible light image generated on the basis of an imagepickup result obtained by the image pickup element for picking up thevisible light image 1051.

Subsequently, a description will be given focusing on a case in whichlaserphyrin is used as a fluorescent material. As depicted in FIG. 7 ,fluorescence emitted from laserphyrin belongs to a visible lightwavelength band, and thus the fluorescence is incident into the camerahead 105 a and is then imaged on the image pickup element for picking upthe visible light image 1051 through the color separation prism 201 aand the short pass filter 211. For this reason, it is possible toobserve a fluorescent image of fluorescence emitted from laserphyrinusing a visible light image generated on the basis of an image pickupresult obtained by the image pickup element for picking up the visiblelight image 1051.

Note that, in a case in which light in a wavelength band in the vicinityof an R component (for example, excitation light having a wavelength of664 nm) is used as excitation light of a fluorescent material emittingfluorescence belonging to a visible light wavelength band such as 5ALAor laserphyrin, the notch filter 1055 blocking light belonging to anexcitation wavelength of the fluorescent material may be mounted on thecamera head 105 a. Similarly, it is also possible to use excitationlight having a wavelength of 405 nm as excitation light of laserphyrin.In this case, the notch filter 1055 blocking the excitation light (thatis, light having a wavelength of 405 nm) may be mounted on the camerahead 105 a, or a long pass filter may be mounted on the camera head 105a instead of the notch filter 1055. With such a configuration, it ispossible to prevent the incidence of the excitation light into thecamera head 105 a.

Spectral characteristics of the dichroic film 203, the notch filter1055, the short pass filter 211, and the long pass filter 213 in thecamera head 105 a have been described above with reference to FIG. 7 .

3.3. Configuration Example 2 of Two-Plate Type Camera Head

Subsequently, as another example of a configuration of a camera head inthe imaging system according to the present embodiment, reference willbe made to FIG. 8 to describe as another example of a configuration of atwo-plate type camera head, particularly, focusing on a configurationuntil incident light is imaged on an image pickup element through abranching optical system. FIG. 8 is a schematic view depicting anotherexample of a configuration of a camera head according to the presentembodiment. Note that, in the following description, the camera head 105depicted in FIG. 8 may be referred to as “a camera head 105 b” in a casein which the camera head 105 is expressly shown.

As depicted in FIG. 8 , the camera head 105 b includes a colorseparation prism 201 b, an image pickup element for picking up thevisible light image 1051, an image pickup element for picking up thenear-infrared light image 1052, a short pass filter 211, and a bandpassfilter 215. Note that the color separation prism 201 b has the sameconfiguration as that of the color separation prism 201 a described withreference to FIG. 6 , and is equivalent to an example of the branchingoptical system 201 depicted in FIG. 4 . That is, the camera head 105 bdepicted in FIG. 8 is different from the camera head 105 a describedwith reference to FIG. 6 in that the camera head 105 b does not includea notch filter 1055 and includes the bandpass filter 215 instead of along pass filter 213. Consequently, in the present description, aconfiguration of the camera head 105 b will be described focusing ondifferences from the camera head 105 a depicted in FIG. 6 , and adetailed description of the same configuration as that of the camerahead 105 a will be omitted.

As described above, in the camera head 105 b, the bandpass filter 215 isprovided in a light path of light which is separated by the dichroicfilm 203 and is imaged on the image pickup element for picking up thenear-infrared light image 1052. The bandpass filter 215 has acharacteristic of transmitting light in at least a portion of awavelength band of the predetermined wavelength band in a near-infraredwavelength band in accordance with a characteristic of a fluorescentmaterial emitting fluorescence in the predetermined wavelength band andblocking light in the other wavelength bands. As a specific example, ina case of focusing on fluorescence emitted from ICG, the bandpass filter215 may have a characteristic of transmitting light in a wavelength band(for example, a wavelength band of 820 nm to 850 nm) of approximately820 nm which is a wavelength band of fluorescence emitted from ICG andblocking light in the other wavelength bands.

In this manner, in the camera head 105 b, the bandpass filter 215 isprovided at the front stage of the image pickup element for picking upthe near-infrared light image 1052. For this reason, the camera head 105b can block excitation light of a fluorescent material such as ICG bythe bandpass filter 215 even when the notch filter 1055 is not providedas in the camera head 105 a in a case of focusing on fluorescencebelonging to a near-infrared wavelength band and emitted from thefluorescent material. Note that the configuration of the camera headdescribed in FIG. 8 is merely an example, and is not necessarily limitedto the example depicted in FIG. 8 . For example, the installationposition of the image pickup element for picking up the visible lightimage 1051 and the installation position of the image pickup element forpicking up the near-infrared light image 1052 may be reversed. In thiscase, for example, as the dichroic film 203, a dichroic film having acharacteristic of transmitting light belonging to a visible lightwavelength band and reflecting light belonging to a near-infraredwavelength band may be applied. That is, the characteristic of thedichroic film 203 may be appropriately changed in accordance with arelationship between the installation position of the image pickupelement for picking up the visible light image 1051 and the installationposition of the image pickup element for picking up the near-infraredlight image 1052.

Subsequently, spectral characteristics of the dichroic film 203, theshort pass filter 211, and the bandpass filter 215 in the camera head105 b will be described with reference to FIG. 9 . FIG. 9 is a viewdepicting another example of a relationship between spectralcharacteristics of a dichroic film and various filters according to thepresent embodiment and a spectrum of light emitted from a light sourceapparatus. For example, in the upper drawing of FIG. 9 , spectralcharacteristics of the dichroic film 203, the short pass filter 211, andthe bandpass filter 215 a re schematically depicted. In addition, thelower drawing of FIG. 9 depicts a spectrum of light emitted from a lightsource apparatus according to the present embodiment. Note that thehorizontal axis and the vertical axis in each of the upper drawing andthe lower drawing in FIG. 9 are the same as those in the exampledepicted in FIG. 7 . Further, in the example depicted in FIG. 9 , thesame light source apparatus as that in the example depicted in FIG. 7 isused. For this reason, the lower drawing of FIG. 9 is the same as thelower drawing of FIG. 7 .

As described above, the camera head 105 b depicted in FIG. 8 isdifferent from the camera head 105 a depicted in FIG. 6 in that thecamera head 105 b does not include the notch filter 1055 and includesthe bandpass filter 215 instead of the long pass filter 213. In otherwords, the camera head 105 b is the same as the case of the camera head105 a with regard to characteristics of the dichroic film 203 and theshort pass filter 211. Consequently, in the present description, adescription will be mainly given focusing on influence exerted due tothe notch filter 1055 not being provided and a characteristic of thebandpass filter 215, and a detailed description of the same portion asthat of the camera head 105 a will be omitted.

In FIG. 9 , regarding a band shown as a characteristic of an ICG-onlybandpass filter, a wavelength band of each of light passing through thebandpass filter 215 depicted in FIG. 8 and light blocked by the bandpassfilter 215 is schematically depicted. As described above, the bandpassfilter 215 has a characteristic of transmitting light in at least aportion of a wavelength band of a predetermined wavelength band in anear-infrared wavelength band in accordance with a characteristic of afluorescent material emitting fluorescence in the predeterminedwavelength band and blocking light in the other wavelength bands. Forthis reason, in a case in which the bandpass filter 215 is provided onthe assumption that ICG is used, the bandpass filter has acharacteristic of transmitting light in a wavelength band (for example,a wavelength band of 820 nm to 850 nm) of approximately 820 nm which isa wavelength band of fluorescence emitted from ICG and blocking light inthe other wavelength bands.

With the above-described configuration, in a case in which ICG is usedas a fluorescent material, fluorescence emitted from ICG is incidentinto the camera head 105 b and is then imaged on the image pickupelement for picking up the near-infrared light image 1052 through thecolor separation prism 201 b and the bandpass filter 215. Note that, asdescribed above, the camera head 105 b does not include a notch filter1055. For this reason, in the camera head 105 b, excitation light of ICGis incident into the camera head 105 b and is guided to the inside ofthe color separation prism 201 b to reach the bandpass filter 215. Onthe other hand, the bandpass filter 215 is provided at the front stageof the image pickup element for picking up the near-infrared light image1052, so that excitation light of ICG is blocked by the bandpass filter215. With such a configuration, it is possible to observe a fluorescentimage of fluorescence emitted from ICG using a near-infrared light imagegenerated on the basis of an image pickup result obtained by the imagepickup element for picking up the near-infrared light image 1052.

Note that, since a case in which fluorescent images of 5ALA andlaserphyrin are observed is the same as the case of the camera head 105a described with reference to FIG. 7 , a detailed description thereofwill be omitted. On the other hand, in a case in which light in awavelength band in the vicinity of an R component (for example,excitation light having a wavelength of 664 nm) is used as excitationlight of a fluorescent material emitting fluorescence belonging to avisible light wavelength band such as 5ALA or laserphyrin, the notchfilter 1055 blocking light belonging to an excitation wavelength of thefluorescent material may be mounted on the camera head 105 b. Similarly,also in a case in which excitation light having a wavelength of 405 nmis used as excitation light of laserphyrin, the notch filter 1055blocking the excitation light (that is, light having a wavelength of 405nm) may be mounted on the camera head 105 b, or a long pass filter maybe mounted on the camera head 105 b instead of the notch filter 1055.With such a configuration, it is possible to prevent the incidence ofthe excitation light into the camera head 105 b.

Spectral characteristics of the dichroic film 203, the short pass filter211, and the bandpass filter 215 in the camera head 105 b have beendescribed above with reference to FIG. 9 .

3.4. Configuration Example of Three-Plate Type Camera Head

Subsequently, as another example of a configuration of a camera head inthe imaging system according to the present embodiment, a descriptionwill be given of an example of a configuration of a three-plate typecamera head, particularly, focusing on a configuration until incidentlight is imaged on an image pickup element through a branching opticalsystem. For example, FIG. 10 is a schematic view depicting anotherexample of a configuration of a camera head according to the presentembodiment. Note that, in the following description, the camera head 105depicted in FIG. 10 may be referred to as “a camera head 105 c” in acase in which the camera head 105 is expressly shown.

As illustrated in FIG. 10 , the camera head 105 c includes a colorseparation prism 201 c, a first image pickup element for picking up thevisible light image 1051 a, a second image pickup element for picking upthe visible light image 1051 b, an image pickup element for picking upthe near-infrared light image 1052, and bandpass filters 233, 235, and237.

The color separation prism 201 c is an optical member that separatesincident light incident on the camera head 105 c into light belonging toa visible light wavelength band and light belonging to a near-infraredwavelength band and then further separates the light belonging to avisible light wavelength band into light belonging to a long wavelengthband including an R component and light belonging to a short wavelengthband including a G component and a B component. Note that the colorseparation prism 201 c is equivalent to another example of the branchingoptical system 201 depicted in FIG. 4 . Specifically, dichroic films 223and 225 are provided inside the color separation prism 201 c. Thedichroic film 223 is a dichroic film for separating light belonging to avisible light wavelength band and light belonging to a near-infraredwavelength band from each other. In addition, the dichroic film 225 is adichroic film for separating the light belonging to a visible lightwavelength band into light belonging to a wavelength band on a longwavelength side including an R component and light belonging to awavelength band on a short wavelength side including a G component and aB component.

More specifically, as depicted in FIG. 10 , the color separation prism201 c is a prism in which a first prism 227 and a second prism 229 arebonded to each other through the dichroic film 223 and a second prism229 and a third prism 231 are bonded to each other through the dichroicfilm 225. That is, the dichroic film 223 is provided at an interfacebetween the first prism 227 and the second prism 229. In addition, thedichroic film 225 is provided at an interface between the second prism229 and the third prism 231.

The dichroic film 223 is an optical film that separates incident lightincident on the color separation prism 201 c and including lightbelonging to a visible light wavelength band and light belonging to anear-infrared wavelength band into light belonging to a visible lightwavelength band and light belonging to a near-infrared wavelength band.Specifically, the dichroic film 223 has a characteristic of transmittinglight belonging to a visible light wavelength band and reflecting lightbelonging to a near-infrared wavelength band.

In addition, the dichroic film 225 is an optical film that separateslight belonging to a visible light wavelength band which has passedthrough the dichroic film 223 into light belonging to a wavelength bandon a long wavelength side including an R component and light belongingto a wavelength band on a short wavelength side including a G componentand a B component. Specifically, the dichroic film 225 has acharacteristic of reflecting light belonging to a wavelength band on along wavelength side including an R component and transmitting lightbelonging to a wavelength band on a short wavelength side including a Gcomponent and a B component. In addition, as another example, thedichroic film 225 may have a characteristic of transmitting lightbelonging to a wavelength band on a long wavelength side including an Rcomponent and reflecting light belonging to a wavelength band on a shortwavelength side including a G component and a B component.

The first prism 227 is a prism functioning as a light path fornear-infrared light on which light belonging to a visible lightwavelength band and light belonging to a near-infrared wavelength band(that is, incident light) are incident and through which light belongingto a near-infrared wavelength band is guided. In addition, the secondprism 229 is a prism functioning as a light path on which lightbelonging to a visible light wavelength band is incident and throughwhich light belonging to a wavelength band on a long wavelength sideincluding an R component in the visible light wavelength band is guided.In addition, the third prism 231 is a prism functioning as a light paththrough which light belonging to a wavelength band on a short wavelengthside including a G component and a B component in the visible lightwavelength band is guided.

Incident light incident on the first prism 227 travels straight insidethe first prism 227 and is separated into light belonging to a visiblelight wavelength band and light belonging to a near-infrared wavelengthband by the dichroic film 223 which is obliquely provided on the opticalaxis thereof.

The light belonging to a near-infrared wavelength band is reflected bythe dichroic film 223 and is guided to the inside of the first prism227. Here, the reflected and separated light belonging to anear-infrared wavelength band (that is, a near infrared ray) is totallyreflected at a position A depicted in FIG. 10 only once and istransmitted to the outside of the first prism 227. Thereby, it ispossible to bring an angle of a film formation surface of the dichroicfilm 223 with respect to the optical axis close to a right angle.Conversely, an installation angle on the optical axis of the dichroicfilm 223 according to the present embodiment is set such that a totalreflection condition of visible rays at the position A is established.The dichroic film 223 is disposed in this manner, so that it is possibleto suppress changes in spectral characteristics of the dichroic film 203due to a difference in an incidence angle between an upper light beamand a lower light beam and to perform wavelength separation with a highlevel of accuracy even when a bright light beam having an F value isincident on the first prism 205.

Near infrared rays having passed through the first prism 227 are guidedto the image pickup element for picking up the near-infrared light image1052. In this case, the bandpass filter 233 is provided in a light pathof light which is separated by the dichroic film 223 and is imaged onthe image pickup element for picking up the near-infrared light image1052. Note that the characteristic of the bandpass filter 233 is thesame as that of the bandpass filter 215 described with reference to FIG.8 . That is, in a case of focusing on fluorescence emitted from ICG thebandpass filter 233 may have a characteristic of transmitting light in awavelength band (for example, a wavelength band of 820 nm to 850 nm) ofapproximately 820 nm which is a wavelength band of fluorescence emittedfrom ICG and blocking light in the other wavelength bands. With such aconfiguration, it is possible to extract only noticed fluorescence inthe light belonging to a near-infrared wavelength band separated by thedichroic film 214. Note that the long pass filter 213 described withreference to FIG. 6 may be provided instead of the bandpass filter 233.In this case, a notch filter 1055 may be mounted at the front stage ofthe color separation prism 201 c.

In addition, light belonging to a visible light wavelength band whichhas passed through the dichroic film 223 is incident into the secondprism 229. In addition, the light belonging to a visible lightwavelength band travels straight inside the second prism 229 and isseparated into light belonging to a wavelength band on a long wavelengthside including an R component and light belonging to a wavelength bandon a short wavelength side including a G component and a B component inthe visible light wavelength band by the dichroic film 225 which isobliquely provided on the optical axis thereof.

The light belonging to the wavelength band on the long wavelength sideincluding the R component is reflected by the dichroic film 225 and isguided to the inside of the second prism 229. An end surface (in otherwords, an emitting surface on a downstream side of the optical axis ofthe second prism 229) on a side opposite to the side where the dichroicfilm 225 is provided in the second prism 229 is provided so as to beperpendicular to the optical axis. For this reason, the light belongingto the wavelength band on the long wavelength side including the Rcomponent is transmitted to the outside of the second prism 229 whilemaintaining a state where the light is perpendicular to the emittingsurface of the second prism 229.

The light belonging to the wavelength band on the long wavelength sideincluding the R component and having passed through the second prism 229is guided to the first image pickup element for picking up the visiblelight image 1051 a. In this case, a bandpass filter 235 is provided in alight path of light which is separated by the dichroic film 225 and isimaged on the first image pickup element for picking up the visiblelight image 1051 a. The bandpass filter 235 has a characteristic oftransmitting light in a wavelength band on a long wavelength sideincluding an R component and blocking light in the other wavelengthbands in a visible light wavelength band. As a specific example, thebandpass filter 235 may have a characteristic of transmitting light in awavelength band of 600 nm to 750 nm and blocking light in the otherwavelength bands. With such a configuration, it is possible to excludelight in wavelength bands other than the wavelength band on a longwavelength side including an R component which is included in lightseparated by the dichroic film 225 (that is, light reflected by thedichroic film 225).

On the other hand, the light belonging to the wavelength band on theshort wavelength side including the G component and the B component andhaving passed through the dichroic film 225 is incident on the thirdprism 231 and travels straight inside the third prism 231. An endsurface (in other words, an emitting surface on a downstream side of theoptical axis of the third prism 231) on a side opposite to the sidewhere the dichroic film 225 is provided in the third prism 231 isprovided so as to be perpendicular to the optical axis. For this reason,the light belonging to the wavelength band on the short wavelength sideincluding the G component and the B component is transmitted to theoutside of the third prism 231 while maintaining a state where the lightis perpendicular to the emitting surface of the third prism 231.

The light belonging to the wavelength band on the short wavelength sideincluding the G component and the B component and having passed throughthe third prism 231 is guided to the second image pickup element forpicking up the visible light image 1051 b. In this case, a bandpassfilter 237 is provided in a light path of light which is separated bythe dichroic film 225 and is imaged on the second image pickup elementfor picking up the visible light image 1051 b. The bandpass filter 237has a characteristic of transmitting light in a wavelength band on ashort wavelength side including a B component and a G component andblocking light in the other wavelength bands in a visible lightwavelength band. As a specific example, the bandpass filter 237 may havea characteristic of transmitting light in a wavelength band of 350 nm to600 nm and blocking light in the other wavelength bands. With such aconfiguration, it is possible to exclude light in wavelength bands otherthan the wavelength band on a short wavelength side including a Bcomponent and a G component which is included in light separated by thedichroic film 225 (that is, light having passed through the dichroicfilm 225).

Note that a material of the color separation prism 201 c according tothe present embodiment is not particularly limited, and it is possibleto appropriately use known optical glass or optical crystal inaccordance with a wavelength of light guided to the inside of the colorseparation prism 201 c.

The first image pickup element for picking up the visible light image1051 a is provided at the succeeding stage of the color separation prism201 c and the bandpass filter 235. That is, light, separated by thecolor separation prism 201 c and having passed through the bandpassfilter 235, in a wavelength band on a long wavelength side including anR component in a visible light wavelength band is imaged on the firstimage pickup element for picking up the visible light image 1051 a. Notethat fluorescence emitted from 5ALA or laserphyrin belongs to awavelength band on a long wavelength side including an R component in avisible light wavelength band. That is, the fluorescence emitted from5ALA or laserphyrin is also imaged on the first image pickup element forpicking up the visible light image 1051 a. From such a characteristic,it is preferable that an image pickup element having higher sensitivitybe applied as the first image pickup element for picking up the visiblelight image 1051 a, and for example, an image pickup element, such as aCCD or a CMOS, which is not provided with a color filter and the likemay be applied.

The second image pickup element for picking up the visible light image1051 b is provided at the succeeding stage of the color separation prism201 c and the bandpass filter 237. That is, light, separated by thecolor separation prism 201 c and having passed through the bandpassfilter 237, in a wavelength band on a short wavelength side including aG component and a B component in a visible light wavelength band isimaged on the second image pickup element for picking up the visiblelight image 1051 b. As the second image pickup element for picking upthe visible light image 1051 b, for example, an image pickup element,such as a CCD or a CMOS, which includes an RGB color filter can beapplied.

The image pickup element for picking up the near-infrared light image1052 is provided at the succeeding stage of the color separation prism201 c and the bandpass filter 233. That is, light separated by the colorseparation prism 201 c and having passed through the bandpass filter233, that is, light in at least a portion of a wavelength band offluorescence emitted from a predetermined fluorescent material (forexample, ICG) is imaged on the image pickup element for picking up thenear-infrared light image 1052. From such a characteristic, it ispreferable that an image pickup element having higher sensitivity beapplied as the image pickup element for picking up the near-infraredlight image 1052, and for example, an image pickup element, such as aCCD or a CMOS, which is not provided with a color filter and the likemay be applied.

As another example of a configuration of a camera head in the imagingsystem according to the present embodiment, reference has been made toFIG. 10 above to describe an example of a configuration of a three-platetype camera head, particularly, focusing on a configuration untilincident light is imaged on an image pickup element through a branchingoptical system.

Subsequently, spectral characteristics of each of the dichroic films 223and 225 and the bandpass filters 233, 235, and 237 in the camera head105 c will be described with reference to FIG. 11 . FIG. 11 is a viewdepicting another example of a relationship between spectralcharacteristics of a dichroic film and various filters according to thepresent embodiment and a spectrum of light emitted from a light sourceapparatus. For example, in the upper drawing of FIG. 11 , spectralcharacteristics of each of the dichroic film 223 and the bandpassfilters 233, 235, and 237 are schematically depicted. Note that, in theupper drawing of FIG. 11 , spectral characteristics of the dichroic film225 are not depicted in order to avoid complication of the drawing. Inaddition, the lower drawing of FIG. 11 depicts a spectrum of lightemitted from the light source apparatus according to the presentembodiment. Note that the horizontal axis and the vertical axis in eachof the upper drawing and the lower drawing in FIG. 11 are the same asthose in the example depicted in FIG. 7 . Further, in the exampledepicted in FIG. 11 , the same light source apparatus as that in theexample depicted in FIG. 7 is used. For this reason, the lower drawingin FIG. 11 is the same as the lower drawing in FIG. 7 .

In FIG. 11 , a graph plotted as dichroic film characteristicsschematically depicts a wavelength band of each of light reflected bythe dichroic film 223 depicted in FIG. 10 and light passing through thedichroic film 223. Specifically, the inner side of the graph plotted asdichroic film characteristics is equivalent to a component passingthrough the dichroic film 223, and the outer side of the graph isequivalent to a component reflected by the dichroic film 223. That is,the dichroic film 223 has a characteristic of transmitting most (forexample, equal to or greater than 90%) of light in a wavelength band of350 nm to 750 nm and reflecting most (for example, equal to or greaterthan 90%) of light in a wavelength band exceeding 750 nm.

In addition, as described above, the dichroic film 225 reflects lightbelonging to a wavelength band on a long wavelength side including an Rcomponent and transmits light belonging to a wavelength band on a shortwavelength side including a G component and a B component in lightbelonging to a visible light wavelength band. As a more specificexample, the dichroic film 225 may have a characteristic of reflectingmost (for example, equal to or greater than 90%) of light in awavelength band of 600 nm to 750 nm and transmitting most (for example,equal to or greater than 90%) of light in a wavelength band of 350 nm to600 nm in light in a wavelength band of 350 nm to 750 nm.

Further, in FIG. 11 , a graph plotted as first bandpass filtercharacteristics schematically depicts a wavelength band of each of lightpassing through the bandpass filter 235 depicted in FIG. 10 and lightblocked by the bandpass filter 235. As described above, for example, thebandpass filter 235 transmits light in a wavelength band of 600 nm to750 nm and blocks light in the other wavelength bands. With such aconfiguration, for example, it is possible to image light in awavelength band on a long wavelength side including an R component, inlight belonging to a visible light wavelength band and emitted from thevisible light source 1431 of the light source apparatus 143 and guidedto the inside of the camera head 105 c, on the first image pickupelement for picking up the visible light image 1051 a.

Further, in FIG. 11 , a graph plotted as second bandpass filtercharacteristics schematically depicts a wavelength band of each of lightpassing through the bandpass filter 237 depicted in FIG. 10 and lightblocked by the bandpass filter 237. As described above, for example, thebandpass filter 237 transmits light in a wavelength band of 350 nm to600 nm and blocks light in the other wavelength bands. With such aconfiguration, for example, it is possible to image light in awavelength band on a short wavelength side including a G component and aB component, in light belonging to a visible light wavelength band andemitted from the visible light source 1431 of the light source apparatus143 and guided to the inside of the camera head 105 c, on the secondimage pickup element for picking up the visible light image 1051 b.

Further, in FIG. 11 , regarding a band shown as a characteristic of anICG-only bandpass filter, a wavelength band of each of light passingthrough the bandpass filter 233 depicted in FIG. 8 and light blocked bythe bandpass filter 233 is schematically depicted. As described above,the bandpass filter 233 has a characteristic of transmitting light in atleast a portion of a wavelength band of a predetermined wavelength bandin a near-infrared wavelength band in accordance with a characteristicof a fluorescent material emitting fluorescence in the predeterminedwavelength band and blocking light in the other wavelength bands. Forthis reason, in a case in which the bandpass filter 233 is provided onthe assumption that ICG is used, the bandpass filter has acharacteristic of transmitting light in a wavelength band (for example,a wavelength band of 820 nm to 850 nm) of approximately 820 nm which isa wavelength band of fluorescence emitted from ICG and blocking light inthe other wavelength bands.

Based on the above-described configuration, the camera head 105 c canpick up, for example, a fluorescent image of fluorescence belonging to anear-infrared wavelength band and emitted from a fluorescent materialsuch as ICG or a fluorescent image of fluorescence belonging to avisible light wavelength band and emitted from a fluorescent materialsuch as 5ALA and laserphyrin.

As a specific example, a description will be given focusing on a case inwhich ICG is used as a fluorescent material. Since fluorescence emittedfrom ICG belongs to a near-infrared wavelength band, the fluorescence isincident into the camera head 105 c and is then imaged on the imagepickup element for picking up the near-infrared light image 1052 throughthe color separation prism 201 c and the bandpass filter 233. Note thatthe camera head 105 c does not include a notch filter 1055, similar tothe camera head 105 b described with reference to FIG. 8 . For thisreason, in the camera head 105 c, excitation light of ICG is incidentinto the camera head 105 c and is guided to the inside of the colorseparation prism 201 c to reach the bandpass filter 233. On the otherhand, the bandpass filter 233 is provided at the front stage of theimage pickup element for picking up the near-infrared light image 1052,so that excitation light of ICG is blocked by the bandpass filter 233.With such a configuration, it is possible to observe a fluorescent imageof fluorescence emitted from ICG using a near-infrared light imagegenerated on the basis of an image pickup result obtained by the imagepickup element for picking up the near-infrared light image 1052.

Subsequently, a description will be given focusing on a case in which5ALA is used as a fluorescent material. As depicted in FIG. 11 ,fluorescence emitted from 5ALA belongs to a wavelength band on a longwavelength side including an R component in a visible light wavelengthband. For this reason, fluorescence emitted from 5ALA is incident intothe camera head 105 c and is then imaged on the first image pickupelement for picking up the visible light image 1051 a through the colorseparation prism 201 a and the bandpass filter 235. In addition, in acase in which a fluorescent image of fluorescence emitted from 5ALA ispicked up, at least the output of an R component emitted from an RGBlaser light source of the visible light source 1431, in light belongingto a visible light wavelength band and emitted from the visible lightsource 1431 of the light source apparatus 143, may be limited (forexample, set to be in an off-state). Based on such a configuration andcontrol, it is possible to observe a fluorescent image of fluorescenceemitted from 5ALA using a visible light image generated on the basis ofan image pickup result obtained by the first image pickup element forpicking up the visible light image 1051 a.

Subsequently, a description will be given focusing on a case in whichlaserphyrin is used as a fluorescent material. As depicted in FIG. 11 ,fluorescence emitted from laserphyrin belongs to a wavelength band on along wavelength side including an R component in a visible lightwavelength band. For this reason, fluorescence emitted from laserphyrinis incident into the camera head 105 c and is then imaged on the firstimage pickup element for picking up the visible light image 1051 athrough the color separation prism 201 a and the bandpass filter 235.For this reason, it is possible to observe a fluorescent image offluorescence emitted from laserphyrin using a visible light imagegenerated on the basis of an image pickup result obtained by the firstimage pickup element for picking up the visible light image 1051 a.

Note that, in a case in which light in a wavelength band in the vicinityof an R component (for example, excitation light having a wavelength of664 nm) is used as excitation light of a fluorescent material emittingfluorescence belonging to a visible light wavelength band such as 5ALAor laserphyrin, the notch filter 1055 blocking light belonging to anexcitation wavelength of the fluorescent material may be mounted on thecamera head 105 c. Similarly, also in a case in which excitation lighthaving a wavelength of 405 nm is used as excitation light oflaserphyrin, the notch filter 1055 blocking the excitation light (thatis, light having a wavelength of 405 nm) may be mounted on the camerahead 105 c or a long pass filter may be mounted on the camera head 105 cinstead of the notch filter 1055. With such a configuration, it ispossible to prevent the incidence of the excitation light into thecamera head 105 c.

Subsequently, a case in which a visible light image of an image pickuptarget is observed using the camera head 105 c will be described. Asdescribed above, in the camera head 105 c, light belonging to awavelength band on a long wavelength side including an R component inlight belonging to a visible light wavelength band is imaged on thefirst image pickup element for picking up the visible light image 1051a, and light belonging to a wavelength band on a short wavelength sideincluding a G component and a B component is imaged on the second imagepickup element for picking up the visible light image 1051 b. For thisreason, for example, the camera head 105 c may generate a visible lightimage of an image pickup target by composing images based on imagepickup results respectively obtained by the first image pickup elementfor picking up the visible light image 1051 a and the second imagepickup element for picking up the visible light image 1051 b.

As described above, in the three-plate type camera head 105 c, a lightbelonging to a visible light wavelength band is separated into lightbelonging to a wavelength band on a long wavelength side including an Rcomponent and light belonging to a wavelength band on a short wavelengthside including a G component and a B component, and the separated lightbeams are respectively imaged on different image pickup elements. Withsuch a configuration, the camera head 105 c can superimpose afluorescent image of fluorescence emitted from a fluorescent materialsuch as 5ALA or laserphyrin on, for example, an image of an image pickuptarget based on the light belonging to the wavelength band on the shortwavelength side including the G component and the B component. Inaddition, the camera head 105 c can perform different image processingon each of the fluorescent image of fluorescence emitted from thefluorescent material such as 5ALA or laserphyrin and the image of theimage pickup target based on the light belonging to the wavelength bandon the short wavelength side including the G component and the Bcomponent.

Spectral characteristics of the dichroic films 223 and 225 and thebandpass filters 233, 235, and 237 in the camera head 105 c have beendescribed above with reference to FIG. 11 .

3.5. Operational Effects

Subsequently, operational effects obtained by applying the imagingsystem according to the present embodiment will be described withreference to FIG. 12 . FIG. 12 is a view depicting characteristics of acamera head according to the present embodiment, and depicts an exampleof sensitivity characteristics for each wavelength of an image pickupelement applied to a camera head such as an endoscopic image pickupsystem and spectral transmission characteristics of a color filterapplied to the image pickup element. In FIG. 12 , the horizontal axisrepresents a wavelength, and the vertical axis represents sensitivitycharacteristics for each wavelength of the image pickup element andspectral transmission characteristics of various filters by a relativevalue (%). Note that, in the example depicted in FIG. 12 , an example ofsensitivity characteristics for each wavelength of a so-called CMOSsensor is depicted as sensitivity characteristics of the image pickupelement. Further, in the example depicted in FIG. 12 , an example ofspectral transmission characteristics is depicted for each of a redfilter, a green filter, and a blue filter as characteristics of a colorfilter.

In addition, among the existing camera heads, in a camera head capableof picking up a visible light image of an image pickup target, an IR cutfilter that cuts infrared light may be provided at the front stage of animage pickup element on which light belonging to a visible lightwavelength band is imaged, in order to improve color reproducibility ofthe visible light image. Based on these points, in order to make iteasier to understand operational effects obtained by applying theimaging system according to the present embodiment, an example ofspectral transmission characteristics of an IR cut filter is alsopresented as a reference in the example depicted in FIG. 12 . Note that,for example, C5000 manufactured by HOYA Corporation or the like is usedas the IR cut filter.

As described above, among fluorescent materials emitting fluorescence ina visible light wavelength band, 5ALA emits fluorescence in a visiblelight region of approximately 635 nm (particularly, a wavelength band ofan R component). In addition, laserphyrin emits fluorescence in thevicinity of a wavelength band of 670 nm to 730 nm, that is, fluorescencein a visible light region (particularly, in the vicinity of anear-infrared region) to a near-infrared region. For this reason, in acase in which a fluorescent image of fluorescence emitted from 5ALA orlaserphyrin is picked up, the fluorescent image is picked up by an imagepickup element on which light belonging to a visible light wavelengthband is imaged.

On the other hand, as depicted in FIG. 12 , an IR cut filter generallytends to have transmittance decreasing in a wavelength band on a longwavelength side including an R component in a visible light wavelengthband. For this reason, for example, transmittance of an IR cut filterdecreases to approximately 40% at a wavelength position of approximately635 nm which is a wavelength of fluorescence emitted from 5ALA. Inaddition, transmittance of an IR cut filter decreases to approximately20% to approximately several % at a wavelength position of 670 nm to 730nm which is a wavelength of fluorescence emitted from laserphyrin.Fluorescence emitted from each fluorescent material tends to have lowerlight intensity than that of other light such as visible rays reflectedby an image pickup target and incident into a camera head and excitationlight of the fluorescent material. For this reason, in a case of aconfiguration in which an IR cut filter is provided at the front stageof an image pickup element, it is difficult to clearly pick up afluorescent image of fluorescence belonging to a visible lightwavelength band and emitted from 5ALA or laserphyrin.

On the other hand, in a camera head according to the present embodiment,an IR cut filter is not provided at the front stage of an image pickupelement picking up an image of light belonging to a visible lightwavelength band, for example, as described above with reference to FIGS.6 to 11 , and a short pass filter or a bandpass filter is providedinstead. That is, in the camera head according to the presentembodiment, it is possible to prevent the occurrence of a situationwhere fluorescence emitted from 5ALA or laserphyrin and guided to theimage pickup element is limited by the IR cut filter when thefluorescence is imaged on the image pickup element. For this reason,according to the camera head of the present embodiment, since it ispossible to more utilize performance of the camera head (particularly,the image pickup element) also in a case in which a fluorescent image offluorescence belonging to a visible light wavelength band is picked up,it is possible to pick up a clearer fluorescent image.

An example of operational effects obtained by applying the imagingsystem according to the present embodiment has been described above withreference to FIG. 12 .

4. EXAMPLE OF HARDWARE CONFIGURATION

Subsequently, an example of a hardware configuration of a so-calledinformation processing apparatus executing various processes like a CCUin the above-described endoscopic image pickup system (that is, theendoscopic surgery system) will be described in detail with reference toFIG. 13 . FIG. 13 is a functional block diagram depicting aconfiguration example of a hardware configuration of an informationprocessing apparatus constituting the endoscopic image pickup systemaccording to the embodiment of the present disclosure.

The information processing apparatus 900 configuring the endoscopicimage pickup system according to the present embodiment mainly includesa CPU 901, a ROM 903, and a RAM 905. The information processingapparatus 900 further includes a host bus 907, a bridge 909, an externalbus 911, an interface 913, an input apparatus 915, an output apparatus917, a storage apparatus 919, a drive 921, a connection port 923, and acommunication apparatus 925.

The CPU 901 functions as an arithmetic processing apparatus and acontrol apparatus, and controls all or some operations of theinformation processing apparatus 900 according to various kinds ofprograms recorded in the ROM 903, the RAM 905, the storage apparatus919, or a removable recording medium 927. The ROM 903 stores a program,an operation parameter, or the like used by the CPU 901. The RAM 905primarily stores a program used by the CPU 901, a parameter thatappropriately changes in execution of a program, or the like. Theabove-mentioned components are connected with one another by the hostbus 907 including an internal bus such as a CPU bus.

The host bus 907 is connected to the external bus 911 such as aperipheral component interconnect/interface (PCI) bus through the bridge909. Further, the input apparatus 915, the output apparatus 917, thestorage apparatus 919, the drive 921, the connection port 923, and thecommunication apparatus 925 are connected to the external bus 911 viathe interface 913.

The input apparatus 915 is an operating means used by the user such as amouse, a keyboard, a touch panel, a button, a switch, a lever, or apedal. For example, the input apparatus 915 may be a remote controlmeans (a so-called remote controller) using infrared light or any otherradio waves, and may be an external connection device 929 such as amobile telephone or a PDA corresponding to an operation of theinformation processing apparatus 900. Further, for example, the inputapparatus 915 includes an input control circuit that generates an inputsignal on the basis of information input by the user using the operatingmeans, and outputs the input signal to the CPU 901. The user of theinformation processing apparatus 900 can input various kinds of data tothe information processing apparatus 900 or instruct the informationprocessing apparatus 900 to perform a processing operation by operatingthe input apparatus 915.

The output apparatus 917 includes an apparatus capable of visually oracoustically notifying the user of the acquired information. As such anapparatus, there are a display apparatus such as a CRT displayapparatus, a liquid crystal display apparatus, a plasma displayapparatus, an EL display apparatus or a lamp, an audio output apparatussuch as a speaker or a headphone, a printer apparatus, and the like. Forexample, the output apparatus 917 outputs a result obtained by variouskinds of processes performed by the information processing apparatus900. Specifically, the display apparatus displays a result obtained byvarious kinds of processes performed by the information processingapparatus 900 in the form of text or an image. Meanwhile, the audiooutput apparatus converts an audio signal including reproduced audiodata, acoustic data, or the like into an analogue signal, and outputsthe analogue signal.

The storage apparatus 919 is a data storage apparatus configured as anexemplary storage section of the information processing apparatus 900.For example, the storage apparatus 919 includes a magnetic storagesection device such as a hard disk drive (HDD), a semiconductor storagedevice, an optical storage device, a magneto optical storage device, orthe like. The storage apparatus 919 stores a program executed by the CPU901, various kinds of data, and the like.

The drive 921 is a recording medium reader/writer, and is equipped in orattached to the information processing apparatus 900. The drive 921reads information stored in the removable recording medium 927 mountedthereon such as a magnetic disk, an optical disc, a magneto opticaldisc, or a semiconductor memory, and outputs the read information to theRAM 905. Further, the drive 921 can write a record in the removablerecording medium 927 mounted thereon such as a magnetic disk, an opticaldisk, a magneto optical disk, or a semiconductor memory. For example,the removable recording medium 927 is a DVD medium, an HD-DVD medium, aBlu-ray (a registered trademark) medium, or the like. Further, theremovable recording medium 927 may be a Compact Flash (CF) (a registeredtrademark), a flash memory, a Secure Digital (SD) memory card, or thelike. Furthermore, for example, the removable recording medium 927 maybe an integrated circuit (IC) card equipped with a non-contact type ICchip, an electronic device, or the like.

The connection port 923 is a port for connecting a device directly withthe information processing apparatus 900. As an example of theconnection port 923, there are a Universal Serial Bus (USB) port, anIEEE1394 port, a Small Computer System Interface (SCSI) port, and thelike. As another example of the connection port 923, there are anRS-232C port, an optical audio terminal, a High-Definition MultimediaInterface (HDMI) (a registered trademark), and the like. As the externalconnection device 929 is connected to the connection port 923, theinformation processing apparatus 900 acquires various kinds of datadirectly from the external connection device 929 or provides variouskinds of data to the external connection device 929.

For example, the communication apparatus 925 is a communicationinterface including a communication device or the like used for aconnection with a communication network (network) 931. For example, thecommunication apparatus 925 is a communication card for a wired orwireless local area network (LAN), Bluetooth (a registered trademark),or wireless USB (WUSB). Further, the communication apparatus 925 may bean optical communication router, an asymmetric digital subscriber line(ADSL) router, various kinds of communication modems, or the like. Forexample, the communication apparatus 925 can transmit or receive asignal to or from the Internet or another communication apparatus, forexample, according to a certain protocol such as TCP/IP. Further, thecommunication network 931 connected to the communication apparatus 925includes a network connected in a wired or wireless manner, and may be,for example, the Internet, a domestic LAN, infrared ray communication,radio wave communication, satellite communication, or the like.

The hardware configuration capable of implementing the functions of theinformation processing apparatus 900 configuring the endoscopic imagepickup system according to an embodiment of the present disclosure hasbeen described above. Each of the above components may be configuredusing a versatile member, and may be configured by hardware specializedfor the function of each component. Thus, the hardware configuration tobe used may be appropriately changed according to a technology levelwhen the present embodiment is carried out. Note that, although notdepicted in FIG. 13 , it obviously includes various kinds of componentscorresponding to the information processing apparatus 900 configuringthe endoscopic image pickup system.

Note that it is possible to create a computer program for implementingthe functions of the information processing apparatus 900 configuringthe endoscopic image pickup system according to the present embodiment,and install the computer program in a personal computer or the like.Furthermore, it is possible to provide a computer readable recordingmedium storing the computer program as well. Examples of the recordingmedium include a magnetic disk, an optical disc, a magneto optical disc,and a flash memory. Further, for example, the computer program may bedelivered via a network without using the recording medium. In addition,the number of computers causing the computer program to be executed isnot particularly limited. For example, the computer program may beexecuted in cooperation of a plurality of computers (for example, aplurality of servers or the like).

5. APPLICATION EXAMPLE

Subsequently, as an application example of the imaging system accordingto the embodiment of the present disclosure, an example of a case inwhich the imaging system is configured as a microscope imaging systemincluding a microscope unit will be described.

For example, FIG. 14 is a view depicting an application example of theimaging system according to the embodiment of the present disclosure,and depicts an example of a schematic configuration of a microscopeimaging system. Specifically, FIG. 14 depicts an example of a case inwhich a video microscope apparatus for surgery including an arm as anapplication example of a case in which the microscope imaging systemaccording to the embodiment of the present disclosure is used.

For example, FIG. 14 schematically depicts a state of a medicaltreatment using the video microscope apparatus for surgery.Specifically, referring to FIG. 14 , a state where a medical doctor whois a surgeon (user) 520 performs surgery on a medical treatment target(patient) 540 on a medical treatment table 530 using an appliance forsurgery 521 such as a scalpel, tweezers, or forceps is depicted. Notethat, in the following description, it is assumed that medical treatmentgenerically refers to various medical treatment, such as surgery orexamination, which is to be performed on a patient who is the medicaltreatment target 540 by the medical doctor who is the user 520. Further,in the example depicted in FIG. 14 , a state of surgery is depicted asan example of medical treatment, but the medical treatment used by thevideo microscope apparatus for surgery 510 is not limited to surgery andmay be various medical treatment.

The video microscope apparatus for surgery 510 is provided beside themedical treatment table 530. The video microscope apparatus for surgery510 includes a base unit 511 serving as a base, an arm unit 512extending from the base unit 511, and an image pickup unit 515 connectedto a distal end of the arm unit 512 as a distal end unit. The arm unit512 includes a plurality of joint portions 513 a, 513 b, and 513 c, aplurality of links 514 a and 514 b connected to each other by the jointportions 513 a and 513 b, and the image pickup unit 515 provided at thedistal end of the arm unit 512. In the example depicted in FIG. 14 , forsimplification, the arm unit 512 includes three joint portions 513 a to513 c and two links 514 a and 514 b. However, actually, in considerationof the degree of freedom of the positions and postures of the arm unit512 and the image pickup unit 515, the number and shapes of the jointportions 513 a to 513 c and the links 514 a and 514 b, the direction ofdriving axes of the joint portions 513 a to 513 c, and the like may beappropriately set so as to realize a desired degree of freedom.

The joint portions 513 a to 513 c have a function of rotatablyconnecting the links 514 a and 514 b to each other, and the driving ofthe arm unit 512 is controlled by driving the rotation of the jointportions 513 a to 513 c. Here, in the following description, theposition of each constituent member of the video microscope apparatusfor surgery 510 means a position (coordinates) in a space defined fordriving control, and the posture of each constituent member means adirection (angle) with respect to any axis in a space defined fordriving control. Further, in the following description, the driving (ordriving control) of the arm unit 512 refers to a change (control of achange) in the position and posture of each constituent member of thearm unit 512 by performing the driving (or driving control) of the jointportions 513 a to 513 c and performing the driving (or driving control)of the joint portions 513 a to 513 c.

The image pickup unit 515 is connected to the distal end of the arm unit512 as a distal end unit. The image pickup unit 515 is a unit thatacquires an image of an image pickup target, and is, for example, acamera capable of picking up a moving image and a still image. Asdepicted in FIG. 14 , the postures and positions of the arm unit 512 andthe image pickup unit 515 are controlled by the video microscopeapparatus for surgery 510 so that the image pickup unit 515 provided atthe distal end of the arm unit 512 picks up an image of a state of amedical treatment region of the medical treatment target 540. Note thata configuration of the image pickup unit 515 connected to the distal endof the arm unit 512 as a distal end unit is not particularly limited,and for example, the image pickup unit 515 is configured as a microscopethat acquires an enlarged image of the image pickup target. In addition,the image pickup unit 515 may be configured to be detachable from thearm unit 512. With such a configuration, for example, the image pickupunit 515 according to usage application may be appropriately connectedto the distal end of the arm unit 512 as a distal end unit. Note that,in the invention, although a description is given focusing on a case inwhich the image pickup unit 515 is applied as a distal end unit, thedistal end unit connected to the distal end of the arm unit 512 is notnecessarily limited to the image pickup unit 515.

In addition, a display apparatus 550 such as a monitor or a display isinstalled at a position facing the user 520. An image of a medicaltreatment region which is picked up by the image pickup unit 515 isdisplayed on a display screen of the display apparatus 550 as anelectronic image. The user 520 performs various treatment while viewingan electronic image of the medical treatment region displayed on thedisplay screen of the display apparatus 550.

With the above-described configuration, it is possible to performsurgery while picking up an image of a medical treatment region by thevideo microscope apparatus for surgery 510.

6. CONCLUSION

As described above, the imaging system according to the presentembodiment includes a light source apparatus that irradiates apredetermined image pickup target with light including a component in atleast a portion of a wavelength band of an excitation wavelength of afluorescent material with respect to each of the plurality of types offluorescent materials. Examples of the plurality of types of fluorescentmaterials include fluorescent materials (for example, ICG and the like)emitting fluorescence belonging to a near-infrared wavelength band andfluorescent materials (for example, 5ALA, laserphyrin, fluorescein, andthe like) emitting fluorescence belonging to a visible light wavelengthband. In addition, the imaging system according to the presentembodiment includes an image pickup apparatus (for example, a camerahead) which picks up an image acquired by a predetermined optical systemunit such as an endoscope unit or a microscope unit. The image pickupapparatus includes a branching optical system (for example, colorseparation prisms 201 a to 201 c or the like) including a dichroic filmwhich separates light belonging to a visible light wavelength band andlight belonging to a near-infrared wavelength band. In addition, theimage pickup apparatus includes a first image pickup element (forexample, the image pickup element for picking up the near-infrared lightimage 1052) which is provided at the succeeding stage of the branchingoptical system and on which light belonging to a near-infraredwavelength band and separated by a dichroic film is imaged, and a secondimage pickup element (for example, the image pickup element for pickingup the visible light image 1051) on which light belonging to a visiblelight wavelength band and separated by the dichroic film is imaged.Based on such a configuration, the imaging system according to thepresent embodiment picks up a fluorescent image of fluorescencebelonging to a near-infrared wavelength band and emitted from ICG or thelike on the first image pickup element side, and picks up a fluorescentimage of fluorescence belonging to a visible light wavelength band andemitted from 5ALA, laserphyrin, fluorescein, or the like on the secondimage pickup element side.

With the above-described configuration, the imaging system according tothe present embodiment can pick up a fluorescent image, corresponding toa fluorescent material to be used, in a more suitable mode even under asituation where a plurality of types of fluorescent materials isselectively used.

Further, as described above, in the image pickup apparatus applied tothe imaging system according to the present embodiment, an IR cut filteris not provided at the front stage of the second image pickup elementpicking up an image of light belonging to a visible light wavelengthband, and a short pass filter or a bandpass filter is provided instead.With such a configuration, it is possible to prevent the occurrence of asituation where fluorescence, belonging to a visible light wavelengthband (particularly, a wavelength band on a long wavelength side), whichis emitted from 5ALA or laserphyrin and is guided to the second imagepickup element is limited by the IR cut filter when the fluorescence isimaged on the second image pickup element. That is, according to theimaging system of the present embodiment, since it is possible to moreutilize performance of the second image pickup apparatus (particularly,the image pickup element) also in a case in which a fluorescent image offluorescence belonging to a visible light wavelength band is picked up,it is possible to pick up a clearer fluorescent image.

The preferred embodiment (s) of the present disclosure has/have beendescribed above with reference to the accompanying drawings, whilst thepresent disclosure is not limited to the above examples. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

Further, the effects described in this specification are merelyillustrative or exemplified effects, and are not limitative. That is,with or in the place of the above effects, the technology according tothe present disclosure may achieve other effects that are clear to thoseskilled in the art from the description of this specification.

Additionally, the present technology may also be configured as below.

-   (1)

An imaging system including:

a light source apparatus which irradiates a predetermined image pickuptarget with light including a component in at least a portion of awavelength band of an excitation wavelength of each of a plurality oftypes of fluorescent materials including a first fluorescent materialemitting fluorescence belonging to a near-infrared wavelength band and asecond fluorescent material emitting fluorescence belonging to a visiblelight wavelength band; and

an image pickup apparatus which picks up an image acquired by apredetermined optical system unit,

in which the image pickup apparatus includes

-   -   a branching optical system that includes a dichroic film        separating the light belonging to the visible light wavelength        band and the light belonging to the near-infrared wavelength        band from each other,    -   a first image pickup element which is provided at a stage after        the branching optical system and on which the light belonging to        the near-infrared wavelength band which is separated by the        dichroic film is imaged, and    -   a second image pickup element which is provided at a stage after        the branching optical system and on which at least a portion of        the light belonging to the visible light wavelength band which        is separated by the dichroic film is imaged,

a fluorescent image of the fluorescence emitted from the firstfluorescent material is picked up by the first image pickup element, and

a fluorescent image of the fluorescence emitted from the secondfluorescent material is picked up by the second image pickup element.

-   (2)

The imaging system according to (1), in which the image pickup apparatusincludes a short pass filter which is disposed in a light path of thelight separated by the dichroic film and imaged on the second imagepickup element, and transmits light having a wavelength equal to or lessthan a wavelength corresponding to a boundary between the visible lightwavelength band and the near-infrared wavelength band.

-   (3)

The imaging system according to (2),

in which the image pickup apparatus includes

-   -   a notch filter which is provided at a stage before the branching        optical system and blocks light in at least a portion of a        wavelength band of the excitation wavelength of the first        fluorescent material, and    -   a long pass filter which is disposed in a light path of the        light separated by the dichroic film and imaged on the first        image pickup element, and transmits light having a wavelength        equal to or greater than the wavelength corresponding to the        boundary.

-   (4)

The imaging system according to (2), in which the image pickup apparatusincludes a bandpass filter which is disposed in a light path of thelight separated by the dichroic film and imaged on the first imagepickup element, transmits light in at least a portion of a wavelengthband of the fluorescence emitted from the first fluorescent material,and blocks light in at least a portion of a wavelength band of theexcitation wavelength of the first fluorescent material.

-   (5)

The imaging system according to (1),

in which the branching optical system includes a second dichroic filmwhich separates the light belonging to the visible light wavelength bandwhich is separated by a first dichroic film serving as the dichroicfilm, into light belonging to a first wavelength band including at leasta portion of a wavelength band of the fluorescence emitted from thesecond fluorescent material and light belonging to a second wavelengthband different from the first wavelength band,

on the second image pickup element, the light belonging to the firstwavelength band which is separated by the second dichroic film is imagedamong the light belonging to the visible light wavelength band which isseparated by the first dichroic film, and

the image pickup apparatus includes

-   -   a third image pickup element on which the light belonging to the        second wavelength band which is separated by the second dichroic        film is imaged, among the light belonging to the visible light        wavelength band which is separated by the first dichroic film    -   a first bandpass filter which is disposed in a light path of the        light which is separated by the first dichroic film and imaged        on the first image pickup element, transmits light in at least a        portion of a wavelength band of the fluorescence emitted from        the first fluorescent material, and blocks light in at least a        portion of a wavelength band of the excitation wavelength of the        first fluorescent material,    -   a second bandpass filter which is disposed in a light path of        the light which is separated by the second dichroic film and        imaged on the second image pickup element and transmits light in        at least a portion of a wavelength band of the first wavelength        band, and    -   a third bandpass filter which is disposed in a light path of the        light which is separated by the second dichroic film and imaged        on the third image pickup element and transmits light in at        least a portion of a wavelength band of the second wavelength        band.

-   (6)

The imaging system according to (5),

in which the first wavelength band is a wavelength band on a longwavelength side including a wavelength band of an R component in thevisible light wavelength band, and

the second wavelength band is a wavelength band on a short wavelengthside including a wavelength band of a G component and a wavelength bandof a B component in the visible light wavelength band.

-   (7)

The imaging system according to any one of (1) to (6),

in which the light source apparatus emits

-   -   first light which is continuously distributed in the visible        light wavelength band and has a peak equal to or greater than a        predetermined threshold value at a predetermined wavelength        position, and    -   second light which includes a component in at least a portion of        a wavelength band of excitation wavelength of the first        fluorescent material in the near-infrared wavelength band.

-   (8)

The imaging system according to (7),

in which the light source apparatus includes

-   -   a first light source unit which emits the first light having the        peak at a plurality of wavelength positions, and    -   a second light source unit which emits the second light, and

the first light source unit is capable of controlling output of lightcorresponding to at least a wavelength position which is included in awavelength band of fluorescence emitted from the second fluorescentmaterial or which is positioned closer to the wavelength band among theplurality of wavelength positions.

-   (9)

The imaging system according to (8),

in which the first light has the peak at respective wavelength positionscorresponding to an R component, a G component, and a B component, and

the first light source unit is capable of controlling output of at leastlight corresponding to the R component in the first light.

-   (10)

The imaging system according to (8) or (9), in which the first lightsource unit is a laser light source.

-   (11)

The imaging system according to any one of (1) to (10), furtherincluding an endoscope unit which includes a lens barrel to be insertedinto a body cavity of an examination subject, as the optical systemunit.

-   (12)

The imaging system according to any one of (1) to (10), including

a microscope unit which acquires an enlarged image of the image pickuptarget, as the optical system unit.

REFERENCE SIGNS LIST

-   100 endoscopic surgery system-   101 endoscope-   103 lens barrel-   105 camera head-   1051 image pickup element for picking up visible light image-   1052 image pickup element for picking up near-infrared light image-   1053 FPGA-   1054 optical system unit-   1055 notch filter-   143 light source apparatus-   1431 visible light source-   1433 near-infrared light source-   201 branching optical system-   203 dichroic film-   205 first prism-   207 second prism-   211 short pass filter-   213 long pass filter-   215 bandpass filter

The invention claimed is:
 1. An imaging system comprising: a lightsource configured to emit light including a component in at least afirst excitation wavelength band to excite a first fluorescence materialemitting a first fluorescence belonging to a near-infrared wavelengthband, and to emit light including a component in at least a secondexcitation wavelength band to excite a second fluorescence materialemitting a second fluorescence belonging to a visible wavelength band; afirst image sensor configured to receive light including a component ofthe wavelength band of the first fluorescence and output a first imagingsignal; a second image sensor configured to receive light including acomponent of the wavelength band of the second fluorescence and output asecond imaging signal; an optical element configured to separate lightincluding the first fluorescence in the near-infrared wavelength bandinto a first optical branch and light including the second fluorescencein the visible wavelength band into a second optical branch; a firstpass filter in the first optical branch configured to transmit lighthaving a near-infrared wavelength band and block light having awavelength equal to or less than a predetermined wavelength belongingthe visible wavelength band; and a second pass filter in the secondoptical branch to transmit light in the visible wavelength band thatincludes red light and block light in the visible wavelength band thatincludes green and blue light.
 2. The imaging system according to claim1, wherein the optical element includes a dichroic film configured totransmit light in the near-infrared wavelength band and reflect light inthe visible wavelength band.
 3. The imaging system according to claim 2,wherein the optical element includes a first prism and a second prism,wherein the dichroic film is between the first prism and the secondprism.
 4. The imaging system according to claim 3, wherein the firstpass filter is a long pass filter.
 5. The imaging system according toclaim 4, wherein the predetermined wavelength is a wavelengthcorresponding to a boundary between the near-infrared wavelength bandand the visible wavelength band.
 6. The imaging system according toclaim 5, further comprising: a notch filter before the dichroic film,the notch filter blocking light in at least a portion of the firstexcitation wavelength band of the first fluorescent material.
 7. Theimaging system according to claim 6, further comprising: wherein thesecond pass filter is a short pass filter that transmits light having awavelength equal to or less than a wavelength corresponding to aboundary between the visible wavelength band and the near-infraredwavelength band.
 8. An endoscope system comprising: a light sourceconfigured to emit light including a component in at least a firstexcitation wavelength band to excite a first fluorescence materialemitting a first fluorescence belonging to a near-infrared wavelengthband, and to emit light including a component in at least a secondexcitation wavelength band to excite a second fluorescence materialemitting a second fluorescence belonging to a visible wavelength band; acamera head including: a first image sensor configured to receive lightincluding a component of the wavelength band of the first fluorescenceand output a first imaging signal, a second image sensor configured toreceive light including a component of the wavelength band of the secondfluorescence and output a second imaging signal, an optical elementconfigured to separate light, received via an endoscope scope, includingthe first fluorescence in the near-infrared wavelength band into a firstoptical branch and light including the second fluorescence in thevisible wavelength band into a second optical branch, a first passfilter in the first optical branch configured to transmit light having anear-infrared wavelength band and block light having a wavelength equalto or less than a predetermined wavelength belonging the visiblewavelength band, and a second pass filter in the second optical branchto transmit light in the visible wavelength band that includes red lightand block light in the visible wavelength band that includes green andblue light; and camera control circuitry configured to obtain a firstfluorescence image signal generated based on a signal from the firstfluorescence captured by the first image sensor or a second fluorescenceimage signal generated based on a signal from the second fluorescencecaptured by the second image sensor.
 9. The endoscope system accordingto claim 8, wherein the optical element includes a dichroic filmconfigured to transmit light in the near-infrared wavelength band andreflect light in the visible wavelength band.
 10. The endoscope systemaccording to claim 9, wherein the optical element includes a first prismand a second prism, wherein the dichroic film is between the first prismand the second prism.
 11. The endoscope system according to claim 10,wherein the first pass filter is a long pass filter.
 12. The endoscopesystem according to claim 11, wherein the predetermined wavelength is awavelength corresponding to a boundary between the near-infraredwavelength band and the visible wavelength band.
 13. The endoscopesystem according to claim 12, further comprising: a notch filter beforethe dichroic film, the notch filter blocking light in at least a portionof the first excitation wavelength band of the first fluorescentmaterial.
 14. The endoscope system according to claim 13, wherein thesecond pass filter is a short pass that transmits light having awavelength equal to or less than a wavelength corresponding to aboundary between the visible wavelength band and the near-infraredwavelength band.
 15. The endoscope system according to claim 8, thecamera control circuitry is further configured to superimpose at leastone of the first fluorescence image signal or the second fluorescenceimage signal onto a visible light image signal.
 16. An endoscope devicecomprising: a camera head including: a first image sensor configured toreceive light including a component of a wavelength band of a firstfluorescence and output a first imaging signal, the first fluorescence,belonging to a near-infrared wavelength band, being emitted from a firstfluorescence material by first excitation light, a second image sensorconfigured to receive light including a component of a wavelength bandof a second fluorescence and output a second imaging signal, the secondfluorescence, belonging to a visible wavelength band, being emitted froma second fluorescence material by second excitation light, an opticalelement configured to separate light, via a scope, including the firstfluorescence in the near-infrared wavelength band into a first opticalbranch and light including the second fluorescence in the visiblewavelength band into a second optical branch, a first pass filter in thefirst optical branch configured to transmit light having a near-infraredwavelength band and block light having a wavelength equal to or lessthan a predetermined wavelength belonging the visible wavelength band,and a second pass filter in the second optical branch to transmit lightin the visible wavelength band that includes red light and block lightin the visible wavelength band that includes green and blue light. 17.The endoscope device according to claim 16, wherein the optical elementincludes a dichroic film configured to transmit light in thenear-infrared wavelength band and reflect light in the visiblewavelength band.
 18. The endoscope device according to claim 17, whereinthe optical element includes a first prism and a second prism, whereinthe dichroic film between the first prism and the second prism.
 19. Theendoscope device according to claim 18, wherein the first pass filter isa long pass filter.
 20. The endoscope device according to claim 19,wherein the predetermined wavelength is a wavelength corresponding to aboundary between the near-infrared wavelength band and the visiblewavelength band.